stupid questions thread

>>8684814
If f has a extremum on a, then [math] f'(a) = 0 [/math].
So solving [math]f'(x) = 0[/math] gives you all the points at which f can possibly reach an extremum.

>>8684814
I'm no mathematician, so I can't explain it with fancy notations

you have a function, derive it. The f'(x) you now get, you equal it to 0, which gives you stationary points, if the derivative (tangent) is 0 it means that the curve is "changing direction"

after you equal it to 0, you get a value, say pi, when x=pi then the equation = 0, right, then you just evaluate it do a "sign study" (dunno the name in english), just a table, for example

x -inf value1 0 value2 +inf
equation.1 + 0 - - -
equation.2 - - 0 + +
equation.n - 0 + 0 -
f'x + 0 0 0 +
fx up min/max up

"0" are your min max, then you take the x value that gave you 0, evaluate it in your original function and you get the y value for that x, and you can draw the graph and shit

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>>8685430
my makeshift table got fucked up, sorry about that

>>8684814
the general rule for this shit:
at points that are local maxima or minima, the derivative must be 0

so you just solve to find when the derivative equals 0, and and you have a small list of points which you can examine one-at-a-time to find out whether they're what you're looking for
some of these will just be local maxima, meaning they're the maximum for their nearby area but there's something higher than them elsewhere in the function. some of them won't be maxima or minima at all. so you need to evaluate all of them individually to see what's up

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Freshman Physicist here. I took a side course in Physical Chemistry, and pic related appears in an explanatory text. Besides chemists being shit at writing, what do they mean by the notation <||> and <|>?

I obviously haven't had any actual QM before, and also I realise the retardation of expecting well-explained QM from chemists.

>>8685454
Bra-ket notation
Its a physics thing actually

1 4 9 16 25
3 5 7 9
2 2 2

>>8685473
I know, as I said, I've only just started, so no serious QM yet. Does Bra-ket only refer to the "mean value"-brackets, or the entire notation with the "|"s?

>>8684814
Search for the extrema of t2-t on [-1;1] and solve for x in cos(x) = t

>>8685596
I meant t^2 - t

>>8685454
[math] | \phi \rangle [/math] is a ket, it's pretty much just a matrix, while [math] \langle \phi | [/math] is a bra, it's dual to the ket. when you see them put together like that, you're taking the inner product of whatever is in between them. It's kind of pointless using bra-ket notation (imo) unless you're actually going to use it, that is, to use it for more than just denoting inner products. But apparently that's just me.

>>8685602
thanks. Seems I'll just have to accept it for now and move on.

I am looking for a way to analyze a set of financial data particularly for a graphing/visualization technique. I have one main grouping of data that represents an indicator to buy or sell. I have an arbitrary amount of different data sets that should corroborate the indicator. Is there a way to visualize or quantify several sets of the corroborating datasets on top of the main indicator dataset? So that when looking through the main indicator and when it's given its signals to buy/sell, can I find a way to graph or visualize many additional data points regarding that data?

>>8685433

Damn you have a nice handwriting. Mine is shitty.

Are ozonides more unstable than superoxides? Wanted to make sure.

>>8685853
hah I wish, I took that from google, mine is beyond horrible, it was just to show the "teckenstudium"

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I need to synthesize this compound, but I'm retarded.

How do I learn how to make tideglusib? I've searched all over the internet hoping to find anything from a well documented procedure to a shake-n-bake style recipe like the kind that meth cooks nervously scribble on loose napkins.

Can someone set me in the right direction in terms of learning just enough chemistry to be able to synthesize this on my own in a home lab environment?

I would just buy it online, but it's like $1000/g and I feel like, while it will take me an incredibly long, painstaking time to learn how to make it myself, it would probably be worth it. Also it genuinely interests me so it's kind of a pet project to motivate myself to learn more.

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>>8686591
Actually I was wrong. It's roughly $3,000/g.

>pic related; more tideglusib to bump my dumb tideglusib question

How much math do I need to know before I stop being a brainlet? I only took calc 1 and 2 because they're mandatory for basically every science degree. I'm a bio grad.

>>8687344
You'd need some solid algebra. Unfornately as a bio grad I think you'll mostly do statistics.

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>>8684814
I have 3 numbers, labelled as
>High:9
>Low:1
>Fraction:0.25
and an output of 3.

3 is 1/4th of the way between 1 and 9. I need to make this into a function but I'm a brainlet and it's making my head hurt.Can anyone help me?

>>8687460
(high-low)*fraction + low

>>8687460
[math]f(x,y,z)=x+z(y-x)[/math]

>>8687476
>>8687487
Thank you very much.

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Any logicians in here?

Consider an interpretation S.

The universe of S is the set of natural numbers

S(P) is the set of even numbers
S(I) is the set of odd numbers
S(Q) is the set of prime numbers
S(R) is the set of multiples of 2

Now, I need to know which objects satisfy these formulas:

(Pa v Ia) = Any object in the universe will satisfy this one

(Qa ^ Pa) = Only the number 2 can satisfy this one, for it is the only even number that is also a prime

(Ra ^ Ia) = No object in the universe can satisfy this formula, since there is no odd number that is also a multiple of 2

(Ia -> ~Ra) = This is the one I'm having problems with, how do I determine which objects satisfy a conditional?

Thank you for your attention.

>>8687515
i have no idea what most of these logic words mean but wouldn't all odd numbers a also satisfy 'not a multiple of 2'?

>>8687515
> (Ia -> ~Ra)
> If a is odd then a is not a multiple of two.

Seems like a tautology to me.

>>8687527
>>8687535
So which objects satisfy that formula? Just the set of odd numbers?

Thanks for your help

>>8687344

A rigorous course in upper division algebra and/or real analysis.

>>8687555
All number satisfy the formula.

A(a) -> B(a) is true if you have both A(a) and B(a), or if A(a) is false (which can be simplified as B(a) or not A(a))

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I am having some doubts while solving pic related.

I understand that its a linear diff. equation and that I can simply use the method of multiplying both sides by a integrating factor.

I am just not quite sure if what I am doing is right. And whats confusing me is the fact that I have a (-1/x) which is what I will integrate.

So how do I solve this one?

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>>8688088
im in differential equations right now, exactly where you're at

i think this is how you do it

>>8688088
you can see my process from top to bottom, left to right

it might be confusing because i use commas

anyways you can see my process for finding the integrating factor without just using the equation

im not sure if it's right though

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>>8688088
sorry last reply

looks like i got it right, pic related, but in the end result it keeps the x times the constant which should just be a constant i think so i dont know if you should keep it

>>8688088
oh shit i just noticed it's an initial value problem

if you plug in pi for x and 0 for y, you get C = -pi

so the actual answer is y = -xcosx - pi
i think

also i should tell you, just in case you don't know, that the point of the integrating factor is so that you can use the quotient rule in reverse

I ate a space cake and just for a laugh I decided to find by trial and error, the value whose log10 is exactly 3.5. Turns out the number is 3162.278.

Is there any significance to this?

>>8688171
>by trial and error
well i guess it signifies the fact that you don't understand logarithms

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I dont really understand the part after ''...by the Chain rule...'' in pic related.

How exactly did he arrive to that?

>>8688490
do you not know what the chain rule is?

>>8688490
In this case you can sort of treat the ratio of differentials as fractions such as (a/b)*(b/c)=(a/c).

This implies that you can do some substitution or change of variables to do whatever it is that you want to do.

>>8688495

well memed anon, you done?

>>8688502
???

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How did he arrive to [3]?

Dumb ESL third worlder here. I'm doing a thermoconductivity test with thermocouples. What is the technical term in English for the thermocouple that meassures the temperature of the air around the sample (as opposed to a contact thermocouple, which touches the sample)?
I am using the term ''ambience thermocouple'', but I feel it's incorrect and google finds nothing about these terms.

>>8688712

Same poster.

So far I think what he did is that he multiplied the root by dx / dt and its basically (dx/dt)^2

This (dx/dt)^2 multiplies the 1 and the (dy/dt)^2 / (dx/dt)^2 and it cancels the denominator. And this would be the result...

Is this even correct or am I just dense as fuck?

>>8688719
>>8688712
sqrt(1+[(dy/dt)/(dx/dt)]^2)dx/dt
=sqrt([dx/dt]^2+[dx/dt]^2[(dy/dt)/(dx/dt)]^2)
=sqrt([dx/dt]^2+(dy/dt)^2)

>>8688731

Thanks mate

>>8688502
because the bit after "then the chain rule gives..." is literally the definition of the chain rule, anon

Do isometries preserve minima of a parabola?

So I made the effort of going through hundreds of course material, solving dozens of example problems and writing a 70 page overview for my probability analysis class and was rewarded with an A+.
The prof made a public list with the results, omitting names (but including student ID numbers).
Today I got an email from one of the failing students asking if I could send her (obviously) a copy of my exam with the answers. I told her no, sent her my 70 page summary instead and suggested (nicely) that she should go over the prof's notes and go over some of the example problems.

What would you have done?
I believe sharing exam answers is immoral, I believe extorting money from them would be immoral (and unsuccessful; there are enough desperate guys out there with decent grades who would happily give out their exams for free) and I would never stick my dick in one of those particular females.

The insulation in a plate capacitor is comprised of two layers with thickness of 1mm and 2 mm, and a relative permittivity of respectively 4 and 6. Calculate the field strength in the thinnest layer when the capacitor is connected to a voltage of 5000V.


The answer is E = 2,14*10^16 volt/meter.

thanks

>>8689110
*How do I solve this?

>>8689110
Look up formula
Plug and chug
Get engineering degree
Suck some cock

Should I even bother understanding what an Equivalent is? Wikipedia says it's an archaic unit of measurement, it makes my head hurt and it seems dumb. Does it have a practical application in chemistry today?

>>8684814

Is x^2 - y^2 a perfect square binomial?

>>8684814
I never bothered to go deep into evolution, and this question is not bait.

I completely get survival of the fittest. But what about traits that aren't necessary to survive, but still are useful? How did they develop (well, mutation, I guess), and more importantly, sustain themselves?

Take for example our teeth: Some people aren't born with wisdom teeth anymore. They are redundant nowadays, but they also don't kill you or make you less suitable a sex partner, especially in modern society. So, how come they disappear anyway?

>>8689214
ya. 1 and 1.

(x + y)(x - y)

How do I write log(200) in terms of log(2) and log(5). Also where can how to solve these problems? For whatever reason I can never wrap my head around logarithmic functions.

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>>8689216

I posted this question on reddit. This is the answer that I got.

>>8686591
>trying to cure your own autism

desu i'll take the bait
>Can someone set me in the right direction in terms of learning just enough chemistry to be able to synthesize this on my own in a home lab environment?
How much chem have you studied up to this point. How much experience do you have with synthesis. How much are you looking to spend on precursors. What kind of lab setup do you have in your garage.

>>8688717

Don't call yourself dumb in a stupid question thread.

>>8689234
From the laws of logarithms
1. log(ab) = log(a) + log(b)
2. log(a/b) = log(a) - log(b)
3. log(a^b) = blog(a)

So in your case:
log(200) = log(2^3 * 5^2)
= 3log(2) + 2log(5)

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>>8686591

How do you pronounce FokI (enzyme)?
>F-O-K-One
>Fok-One
>F-O-K-i
>Foki
>Fok-i
Been working on my bachelors thesis for months now and I'm supposed to keep a presentation about it and I just now figured I have no idea how to say it out loud. The body comes from [F]lavobacterium [ok]eanokoites I'm guessing but I don't know what the "I" is from apart that it's probably a roman numeral 1.

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On pic related I assume he took the derivative to calculate the limit.

But why? Did he really took the derivative? or did he do some re -arrange using some identity I dont know of atm?

>>8689334
No idea, but probably Fok-One. For example, you say Jak-Stat, not jay ay key etc and you should know how restriction enzymes names are formed.

>>8689475
L'Hopital's rule anon

if the limits of f(x) and g(x) both go to 0 (or both to infinity), then lim f(x)/g(x) = lim f'(x)/g'(x)

Can someone explain toe how to solve a Bernoulli linear differential equation?

>>8688300
I get the idea but, yeah, it's not intuitive as to why 3.5 corresponds to that exact figure.

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>>8684814
I'm new to computer programming but this has been bothering me since I started.

I remember reading that when you write a program the compiler takes your code and compresses it, translates it to machine language, sends your code to the CPU, the CPU then executes the instructions as fast as possible.

My question is what the fuck is exactly happening? How is the code compressed, how does my code get translated, what's happening on the hardware exactly, and how do the software and hardware interact?

I remember when I took a few courses in university for my major they just kind of handwaved the whole thing. Obviously I'm not expecting a someone to explain it all here but if you guys could point me in the right direction or some books on the subject that would great

What is the formal definition of implicit differentiation? All textbooks I have read just say to differentiate y like you are differentiating x and then put a y' next to it.

>>8689773
the number whose log10 is 3.5 is just the number you get by taking 10 to the power of 3.5 -- there's no trial and error necessary, you just need to type that one operation into a calculator

you can also look at 10^3.5 like 10^3 * 10^0.5, which is just 1000 * sqrt(10)

>>8689778
I'd recommend starting from the bottom up, are you familiar with things like logic gates and state machines?

>>8689817
I took like three classes in computer programming.

I don't have the slightest idea what you're talking about. Please forgive me I'm an idiot.

>>8689827
You're not an idiot, if you don't know about something, you don't know about it. The important thing is you want to learn, I imagine most people in those classes have the same question and aren't asking.

Logic gates are the basic digital circuit building blocks, here's an okay intro https://www.youtube.com/watch?v=95kv5BF2Z9E

After that start looking at combinational and sequential logic circuits, and finally state machines which a CPU basically is. Then look a little bit at assembly language and instruction set architectures, after that you should have most of what you need.

>>8689803
>1000 * sqrt(10)
Yes that makes sense now. I wanted it broken down like that - and to know the origin of this seemingly arbitrary ratio. It's the square root of 10. Seems obvious now.

what property of algebra allows:

(a + b) + c <---> a + b + c

>>8689717

Thanks friend. Didnt know about that.

>>8689884
Commutativity?

>>8689884
Associativity is
(a + b) + c = a + (b + c)

Since these two are equal, we don't bother with parenthesis to distinguish them, and just write a + b + c (which wouldn't make sense if associativity didn't hold)

>>8689907
>Commutativity

ermm no? commutativity allows for exchange of positions, but what property of algebra allows the neglect of brackets, or order of operations in a sense.

>>8689910

so its "trivial" ??

>>8689916
>so its "trivial" ??

What do you mean by that ?

>>8689929

"well of course (a + b) + c <---> a + b + c how else can it fucking be"

>>8689916
>ermm no?
Fuck you then.

>>8689936
Trivial means something that doesn't hold much information, not something that is easy or "natural".

Anyway, associativity doesn't hold in all algebraic structures. Sometimes, [math] (a + b) + c \not = a + (b + c) [/math] (of course, a, b and c are not "regular numbers")

>>8684814
2cos(x)*(-sin(x)) - (-sin(x)) = sin(x)*(1 - 2cos(x))
we need to find the points where the derivative is 0, as any other points are guaranteed to not be extrema, so x = n*pi, x = pi/3 + 2*n*pi, x = -pi/3 + 2*n*pi. Now, to classify the points, we take the second derivative. 2cos(x)*(-cos(x)) + 2*(-sin(x))*(-sin(x)) - (-cos(x)) = -2cos^2(x) + 2sin^2(x) + cos(x) = 2 - 2cos^2(x) - 2cos^2(x) + cos(x) = -4cos^2(x) + cos(x) + 2. Using the pythagorean theorem, we get (1-sqrt(33))/8 < cos(x) < (1+sqrt(33))/8 is a maximum, and otherwise is a minimum.

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>>8689959

:(

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How can one check if their possibly new results have already been published? I've checked Arxiv, and my searches provided no results, but the uncertainty is still present. Moreover, if I really had come up with something new, could I just upload it there?

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>>8689778

The idea behind a CPU is actually pretty simple.

One one side you have registers (a memory array), and on the other side you have a list of instructions; in between, the CPU.

Instructions are like ; take the number at register 5, add it to the number at register 8, and put the result at register 2 (ADD 5, 8, 2).
There are few other arithmetic instructions, but all work the same way. Then you have instructions to tell you what is the next instruction to read (GOTO and conditional GOTO)

The CPU takes the current instruction, processes it, and then goes to the next one.

Of course in real life things are a lot messier, but that's all there is to the raw principle of CPU.


Compilation is the act of translating from a language into an other (which can be the instruction set of a CPU). So yes it takes your program and makes the same thing using arithmetic operations and goto.

>>8689845
> confirmed for brainlet who doesn't know what a CPU is.

Is a x ^ 0 "actually" 1, or is it just a "definition" - a sort of fudge to make the maths work?

I understand how say 10 ^ 2 is 100 and 10 ^ -2 is 0.01, making it intuitive to say 10 ^ 0 is 1, but is it inherently so, or was it agreed that we'd consider it to be 1 for the above reasons?

>>8690028
So the x^n operation is "n copies of x" times 1 (the multiplicative identity). x^0 is 0 copies of x.

>>8690013
Know your field

>>8690028
>Is a x ^ 0 "actually" 1, or is it just a "definition" - a sort of fudge to make the maths work?

It depends on what your definition of ^ is. But even with the basic definition of x^n is x*x*...*x n times (with n > 0),
it's somewhat natural to say x^0 = 1 because of what you said, so we say it's like so
(but be aware, x^-n is just the same, it was defined to be the inverse of x^n to make things work well, in some way).

We can also define ^ with the exponential function, and then x^0 is defined to be 1 without a need to go further.

>>8690051
Yes, before I'd seen a demonstration of 0.01, 0.1 (negative powers), 1, 10, 100, etc, that would have been my "intuitive" reasoning: that raising to the power of 0 is 0. Just like anything times 0 = 0.

>>8690058
It's not necessarily anything big, and this field is not practiced in my country. Therefore, I have no one to ask about it , and my knowledge is self-obtained. Nevertheless, I put some pieces together and would like to publish my stuff (which itself is correct) if possible.

>>8690071
If it is original work and you believe it to be worthwhile to the field post it. It may turn out that that result has already been found, in that case you have independently verified that result. Ergo it is still worthwhile to post.

>>8685454
Bra ket notation. |Ψ> is a vector, <Ψ1|Ψ2> is a scalar product

>>8690070
x^0 isn't 0 copies of x, it's the "empty product" (it has in fact nothing to do with x, since it's empty). And the empty product must be 1, as you noticed.

In a maybe simpler way, say you multiply x^0 by x^n. That makes it x^(0+n) = x^n.
So x^0 = 1.

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>>8690091
Thank you!

>>8690096
>In a maybe simpler way, say you multiply x^0 by x^n. That makes it x^(0+n) = x^n.
>So x^0 = 1.

But what if n = 0?

>>8690125
Then you must have x^0*x^0=x^(0+0)=x^0. The 1 still works

>>8690133
But we end up back at the original "problem" of why it's 1 in the first place.

>>8690143

What if the value of x^0 has nothing to do with the value of n we used to find it ? Or maybe there's a hidden n in x^0 ?

>>8690028
[math]x^n*x^{-n} = 1[/math]
[math]x^{n+(-n)} = 1[/math]
[math]x^0 = 1[/math]

>>8690143
It's the only number that works for n ≠ 0 and x ≠ 0 in the formula x^n = x^(0+n) = x^0 * x^n and it still works for x^(0+0). More fundamentaly, it's the neutral element for the multiplication

>>8690125
The point is that it holds for all values of n, anon.

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>>8684814
I'm writing an essay on the history of computing

What are some interesting case studies of scientists using electronic computers? Hopefully something between 1940 and 1975? Something that's well documented and the computer was necessary to the science?

>>8690469

frank rosenblatt

>>8690486
(((Rosenblatt)))

>>8688088
In this case you can just rearrange the terms to get d(y/x) / dx = sin(x)

I have some doubts regarding the name of these operations and how one should call them.

When one refers to dy/dx does one say ''the derivative of y with respect to x''?

>>8690954
Yes that's right.

Also, when you take the derivative of a function, this is called "differentiating" it, not "deriving" it, which can be a bit confusing.

>>8691007

Yeah I have to do some presentations and I just don't want to look like a dumbass and want to say things the way they are.

Thanks.

>>8690020
I know that's not really what a CPU is but in terms of giving the person place to look to really understand how code relates to hardware it is better than an abstract overview of what a CPU is, like the RAM model.

Quick QM question: if in a cartesian coordinate system I have the X position operator, ie the operator which does X |x> = x |x>, and also the Y position operator Y |y> = y |y>, is it true that X |y> = 0 and Y |x> = 0 because x and y operators/kets live in different spaces?

can someone tell my whats the main point of quadratic or linear equations is? like, i understand it but i don't know why do i need it for.

How do you determine up-thrust on a body, I've got the volume and dentisty of the water, but I can't find the equation

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Can anybody tell me why he cancelled the Change in T after he got the limit?

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I Didn't know where to share my happiness, but you guys have NO IDEA HOW GOOD THIS FUCKING FEELS.

>>8689215
Redundant teeth need resources and increase vulnerability to infections etc. so they are an evolutionary disadvantage. As to how come they disappear, haha mutations happen, good or bad.

>>8690028
>but is it inherently so, or was it agreed
That is the most important questions off meta-mathematics, which boils down to "is math discovered or invented?".
Because everything could just be a "fudge to make the maths work" or it also could be a constant of our universe.
There really is no answer.

As a though experiment imagine never to have hear about numbers and then opening a analysis textbook which starts by defining what the real numbers are, id imagine that from this point of view everything might seem like things that have been arbitrarily agreed upon.

Same with x^0=1, it has to be true for consitency reasons (the most important thing to guide a mathematician) but this leads to the question wether the mathematics around it are just arbitrarily choosen or universal.

>>8691537
>linear equations
They are quite literallly everywhere.

Most of engineering tries to modell things in a linear way, having a mechanical system will often bring you to a system of linear equtions which you need to solve or calculate eigenvalues etc..

They are also extremly important for computer graphics. 3D animations are represented as matrices, which are just linear functions.

A big part of numerical mathematics is about figuring out how to solve systems of linear equations, because this is neccesarry for all kinds of people, from meterologists to aerospace engineers.

>>8689475
el hospitals rule

>>8691849
Weeb

>>8692009
>A big part of numerical mathematics is about figuring out how to solve systems of linear equations
̶b̶e̶c̶a̶u̶s̶e̶ ̶t̶h̶i̶s̶ ̶i̶s̶ ̶n̶e̶c̶c̶e̶s̶a̶r̶r̶y̶ ̶f̶o̶r̶ ̶a̶l̶l̶ ̶k̶i̶n̶d̶s̶ ̶o̶f̶ ̶p̶e̶o̶p̶l̶e̶,̶ ̶f̶r̶o̶m̶ ̶m̶e̶t̶e̶r̶o̶l̶o̶g̶i̶s̶t̶s̶ ̶t̶o̶ ̶a̶e̶r̶o̶s̶p̶a̶c̶e̶ bec̶e̶n̶g̶i̶n̶e̶e̶r̶s̶.̶
because they are easier to solve, so we model stuff as linear systems

>>8691849
omedetou gozaimasu~
enjoy your new degree in anime

>>8691537
basically math is needed if you want a career in STEM
you can get a job that doesn't involve thinking and become an office drone or a cashier or something instead

>>8692023
Exactly. But I believe it goes both ways.
People modell things as linear systems, because they are easier to solve so mathematicians try to come up with ways to solve them even more efficient, because these methods are in demand.

pls respond to >>8689783

>>8691506
X, Y operators are independent i.e. [X,Y] = 0. This is not the same as saying "they live in different spaces". The state of your system depends on x and y. You should denote eigenstates as |x,y> s.t. X|x,y> = x|x,y> and Y|x,y> = y|x,y>.

>>8689783
>>8692106
Have you seen the chain rule? It's just that

>>8692128
Like [math]\frac{dy}{dy}\frac{dy}{dx}[/math]?

>>8692153
Shit, what went wrong there?

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hello /sci/bros, homies and senpaitachi.

is this proof enough? I am sceptical because I only showed that it can't be in Q, but I don't necessarily prove that it must be in R, just that it can't be in Q. For example, it could be in N, Z or C for all we know.

Can obesity and depression make you dumber?
Just retook an IQ test that I had taken 2 years ago and it was lower by 10 points

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>>8692350

>taking IQ tests

what is wrong with you people

>>8692328
it must be in R because R is closed under addition

it cant be in N or Z because those are both in Q

its in C because R is in C

>>8692351
>frogposting
I could ask you the same question.

>>8692355

well...everything is in Q so what are you even trying to say here?

>>8692361
no, not everything in Q (i.e. sqrt(2))

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I forgot how to do logarithms and I just found a assignment that I had to hand in a while back, how the hell do I solve this myself?

>>8692407
recall that log (a^b) = b * log(a)
the rest should be simple algebra

>>8689845
Usually on sci if you don't preface your questions with "I'm a brainlet/ retard" you get a thousand people descending upon you for not knowing stuff.

Thanks though I'll start looking into it.

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What is the bond disosociation energy of D(HO-OH)? Given the value for the enthalpy of OH is 33.9kJ mol
I keep getting 472 kJmol cause I'm obviously missing something here
And it's probably something super simple and idiotic but help me out anyways?

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>>8684814

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>>8692751
I'm so blonde some times, I got it never mind. ignore me

I'm sure these are common/easy questions, but just for safety:

x±y*0=x
x±y=x/0

Does this work? Is this another reason why x/0 is undefined?

hey guys i'm not sciencefag in the least, in fact i'm borderline retarded
what i'm wondering is you have the type of science where you make a new cpu for the iphone 8, and you get paid by apple. and then you have the type of science where you are making breakthroughs and discoveries and shit, who pays you for that? sorry if question is stupid, pls let me know

Promise this isn't for homework (lol srsly guise).

I'm trying to come up with a probability model for troubleshooting parts in a system.

You have A, B, C, D, E. B through E are paired with A so that is constant throughout all sets (AB, AC, AD, AE).

One or both parts of the set can be good or bad. If one part is bad, the whole set is bad.

Assuming that all of the above sets are bad and failed the test, how do you determine:
1) The probability of A being bad in each set
2) The probability of not-A being bad in each set
3) The probablity of BOTH parts being bad

>>8692753
4 eqn 4 unknown

T = 160k
x = mm fund
y = bond
z = int stock
v = dom stock

4z = v
0.6T = x+y
6.4k = 0.025x + 0.035y + 0.04z + 0.06v
x+y+z+v = T

>>8693156
no that doesn't follow algebra rules you can't do that

>>8693216
if this ends up being still being 50% or maybe some bullshit like a 33% even split i will laugh myself to tears.

i'm just trying to figure out if there's an overall higher probability of A being bad given that it's constant in all four sets, or if that's negated by the potential for both parts of the set being bad.

>>8693224
Can you expand into specifics?

>>8693198
you have to write "grant proposals", which are basically papers asking either the government or some big private donor to give you lots of free money for science purposes by convincing them that the thing you're trying to research is worthwhile

>>8692016
>>8692026
I went from third world south american country shit corrupt uni to japan's osaka university engineering department, I'm happy.
Also only anime i've watched were the ones on tv when I was a kid.

>>8693240
ah
I assumed you were some sort of American weeb moving to japan to live out his dream of making anime real

/sci/, I'm reading this article:
pastebin WvAdkEri (system thinks it's spam when I post the arxiv link)

On page 3, section 2, the author defines A as a L x P matrix. He then goes on to set A_(2i-1,k+P) = 1.

How is this possible if A only has P columns? Am I missing something?

>>8693235
I'm just using + beacuse I don't know how to type the +- thing

x + y*n = x

n necessarily has to be 0 cuz identity (i think)

let's say you're still trying to solve anyway

you have to do the same things to both sides of the equation, if you divide by n it turns into

(x+y*n)/n = x/n

You can't just separate the yn term without it being done to the whole thing.

>>8693237
dang
so realistically on what merits do governments grant proposals?
and who are these "big private donors"
and who writes these proposals? like how are these research teams gathered about and propsals written up in the first place?

>>8692328
>is this proof enough?
Yes.
The number cant be in C because then it has to be in R too.(C means the number can be written as a+bi where a and b are reals, you can choose b=0)

So we know that q is not in irrational, so it has to be either in N, Z or Q, but all of N, Z and Q only contain rational numbers.

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Anyone wanna help?

>>8693406
try taking a non-shitty screenshot with actual readable text

So a way of thinking of derivatives are units of a function per input unit?

e.g units of f(x) per x ?

>>8693406
Here's my attempt. Though you shouldn't post a picture for ants next time.

1. d
Work done is determined by velocity (force*velocity*time), not speed.

2. True

3. False
4. False
(I'm seriously not sure on this one but whatever.)

5. False

6. b
7. a
KE = 0.5*m*v^2

>>8693455
Exactly

But keep in mind that a derivative is always a limit, meanig that to get a slope (which is exactly f(x) per x) at one point you bring you put line through two points of the graph of f(x) and calculate what happens when they gert really close.

>>8693493
I have these holes in my knowledge I never really thought about.

I was pretty amazed when I realized (I think) why taking the derivative of a derivative makes sense. i.e the first derivative can be seen as steepness as a function of say x, and then you just forget about the first function and think of the new steepness of the derivative.

it took me a while and I previously just did things without thinking about why.

I probably still have a lot of things I still do not understand like that.

1. Can you divide meson into single quarks?
2. What will happen if you are going to provide more and more energy to meson?

>>8684814
Question:
Why do people believe Thorium is a cleaner source of energy than uranium?
Thorium turns into Uranium-233. If you take the fission yield curve of U-233 and trace out the decay chains on the chart of nuclides, lo and behold, it produces the same radioactive waste that a traditional U-235 or Pu-239 breeder reactor does.

>>8693529
how are both extracted and enriched?

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Hi guys I have a question regarding regression analysis.

So, I have a model Y = -26.04926 + .7823374*x1

however, after running generalized least squares the constant blows up and the resulting model becomes

124.5887 + .5382145*x1


further, the standard error of the constant term increases from ~5 to ~51


Essentially, what I want to know is what the heck does the change in standard error mean? what causes the increase in the constant?

pls respond

I'm going to start studying at university (not underage, took a three year break after HS). I'm probably going to start a bachelor's degree program of either chemistry or molecular biology. Any opinions (that are not "do something COMPLETELY different")? If that's too little information I can provide more later if someone answers.

I know this is super general but how do I git gud at math? I have been terrible since high school. Please, I just want to graduate college.

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Reposting from dead thread

Would I be stupid to take a full time class load in the summer? I'm finishing my "second" year of college (chose mechanical engineering this year) and I'm pretty behind course-wise

The classes would last for 2 months, each one 5 days a week.

The courses I may take are
Calculus III
Mechanics of materials
Thermofluids
Electromechanical systems


How feasible would it be to take all of these and pass with good grades? I won't be working if I do it

Any tips?

>>8695535
[eqn]pls respond[/eqn]

>>8695658
I did something similar last year. I did fine grade-wise but I was burned out for the first half of fall semester. That hurt my grades, for sure.

>>8695681
So you wouldn't recommend it?

>>8695689
If you are behind to the point of it making it taking longer than 4 years I recommend it.

>>8695648
Do you want to understand maths or just know how do to maths?

>>8695701
Do math. I just want to pass math courses.

>>8695705
Which kind of math courses?

>>8695721
college algebra + trig

>>8695721
I'm sure you'll make fun of me but Algebra for calculus

>>8695698
Pretty much, but do you have any tips then?

>>8695723
>>8695725
Look for a book on Google called "Engineering Mathematics" by Stroud. It is very easy to follow.

Paul's online math notes is also good; http://tutorial.math.lamar.edu/

>>8695742
Thanks pal I'll look into it.
>>8695734
Don't stress out over stupid shit.

>>8695771
Stupid shit such as?

>>8695781
Homework, stuff like that.

>>8695799
thanks pal

What does it mean if the amplitude of an electric organ discharge goes down? Like eels and shit after being amputated. Is the electricity "weaker"?

What is the opposite of applied sciences called.
Research science?
I'm talking about the type where you discover shit, make breakthroughs, add to the collective knowledge etc. etc.
science is also not my area of knowledge but I doubt I needed to clarify that

What do vectors have to do with forces?

>>8697865
Vectors (in R^n) represent something with a magnitude and a direction.

A force has a magnitude (how much force) and a direction (which direction the force is being applied). So you can represent a force by a vector.

I got a task where I need to explain that pV=constant when temperature is constant. I'm horrible at explaining it in a good way even if I get it in my head.

>>8698157
Ideal gas law pv=nrt this isn't particularly hard

what is "industry research"

>>8691849
>Not going to TouDai or KyouDai
On the real though, congrats my guy. Are you taking classes in English or Japanese? Also, major?

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I need to maximize a function under 4 constraints in Excel (or R but preferably Excel) and Im not sure how to do it. I tried using the Solver package but it gave me a nonsensical answer. Maybe I used it wrong? Plz Help

>>8698860
i just tried this and got
8 units of B and
16 units of C

6760 profit

what do you mean by nonsensical answers?

>>8698902
playing with this a bit more, i think i found your nonsense
when adding your solver rules, make sure your product units are constrained to be integers, and also constrained to be greater then or equal to 0

>>8698919
Thank you, I have it set to be positive numbers but I don't see how to restrict the answers to be integers.

>>8699009
Actually this is weird, I figured out how to restrict it to integers and I got B=28 and C = 4 but I also have 6760. I checked the math for both of us and both of our solutions give the same max profit and fit under the constraints.

>>8684814

What causes mechanical vibrations?

I understand that vibration is roughly the same thing as elasticity, so maybe I want to ask it differently:

What physical properties of a material lead to elasticity?

My understanding is that atoms act like little springs and repel each other.

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without using proof by induction, proof the following statement

>>8700134
>My understanding is that atoms act like little springs and repel each other

thats part of it, yes. discontinuities, interstitial atoms in impure substances (alloys), and lattice structures play a part as well.

>>8700139
[math]
n = 2k + 1
n^2 = (2k +1)^2 = 4k^2 + 4k + 1
n^2 = 4k (k+1) +1
[/math]

Now you can separate the cases where k is odd and k isn't.
Unsurprisingly, both work.

>>8700144
Thanks anon. Do you happen to know of an advanced text on vibrations that would give me more detail into my question?

I've completed a course on the topic.

>>8700159

>Mechanical Vibrations: JP Den Hartog
will give a continuous understanding while

>Materials Science and Engineering: Callister

will give you a discrete/chemical understanding.

the books cover LEHI materials almost exclusively, so keep in mind that if you want to learn about vibrations in anything other than metals or concrete, you have a few more textbooks to dig through first.

>>8700139
n = 2k+1 where k is non-negative integer

n^2 = 4k^2+4k+1 = 4k(k+1)+1

If k is even then 4k is divisible by 8

If k is odd then k+1 is even and 4(k+1) is divisible by 8

Thus n^2-1 is always divisible by 8. QED.

>>8684814
>In order to understand why electrons don't collapse inside the nucleus, one can assume that the electrons move along circular paths around it. The resulting centrifugal force holds them at a constant distance from the nucleus provided that the attraction and the centrifugal force cancel each other out.

I know it's in a text book, but it sounds kinda hokey, like one of those things PBS Space Time would lecture you on. Is that really the reason?

>>8700199
Old model that was rekt by QM

>>8700158
>>8700186

boi didnt think about using odd and even property again thanks bros

>>8700199

No, it's pretty much bullshit. 1) Moving in a circle involves acceleration. 2) When charge experiences accelerations, it radiates EM, hence losing energy.

Put 1 & 2 together, and an electron orbiting the nucleus would emit a bit of EM radiation and quickly smash into the nucleus.

>>8700209
>>8700244

Thought so, thanks. Now that I'm looking at it, the textbook says "unaltered edition" on the second page, even though it's recent. Really irresponsible to be teaching students outdated shit.

What major maximizes my chances of being picked up as an astronaut?

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>>8700244
>1) Moving in a circle involves acceleration.

>>8700319

Yeah we can clearly see the ISS isn't subject to acceleration, since it goes on a straight line around the earth

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Should I bother trying to understand every step in a demonstration? Right now I'm with Cauchy stress tensor and I can't see how do you go from

[math](\sigma^*_{nx}-\sigma_{nx})dydz[/math]

to

[math]{\partial\over \partial x}\sigma_{nx}[/math]

knowing that

[math]\sigma^*_{nx}=\sigma_{nx}+{\partial\over \partial x}\sigma_{nx} dx[/math]

Apparently there's also some "divide by [math]dxdydz[/math] at the end" and I don't even know if that's rigorous.


So this is really interesting but I don't think it's practical, maybe I should just memorize the matrices.

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how do i solve this problem? do i just turn the resistor RL into an open circuit and short circuit and solve for the respective values?

>>8700319
what do you think gravity is doing to that thing nigga

to be in orbit around a planet you must be constantly accelerating downwards

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Brainlet here. Did I do it right or did I goof? Need to answer in exact form.
Love you /sci/. N-n-no homo.

If i have a function f(x) and the Hessian matrix of an extremas eigenvalues have a 0, how would I go about determining what kind of extrema the point is?

>>8700582
Dig deeper.

>>8700585
wot.

>>8700587
I've never done this in multidimension, but for a one dimension curve you have to find the first non-nul derivative. I guess you'll have to find the third-order derivative and do stuff with it.

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I can't decide whether I want to do Astrophysics, Astrobiology, Marine biology, or Palaentology as a degree at uni because I'm interested in all those subjects
What courses should I do first year that enable me to choose one of these 4 degrees specifically in the second year?

How the fuck is 0^0

>>8701219
Don't choose a major first. Choose courses first and then let your course choices lead you into your field. First year is general stuff anyways. Just take calc 1 and 2, general chem, intro bio, intro physics, and maybe a history course.

>>8700576
G-g-guys help

Quick questions. A book is asking me to prove the nested interval property assuming only the bolzano-weierstrass theorem.

Is this the proof:

Let [an,bn] be the sequence of intervals
the sequence
a1,a2,a3,... is bounded (easy to prove)
b1,b2,b3,... is bounded (easy to prove)

Thus by the bolzano-weierstrass theorem there exists a subsequence of both an and bn that converges to limit

Pick such a sequence for the a's, say
a1, a54, a666, a878, etc.

And then from the subsequence
b1,b54,b666,b878,... pick a subsequence here that converges (apply bolzano-weierstrass again, just in case)

Then use that sub-subsequence to craft a new. Then say that the limit of the a's is a and the limit of the b's is b. Then the infinite intersection would be [a,b]

But using some set theory we can show that the original intersection of [a1,b1] , [a2,b2, [a3,b3],... is actually equivalent to our new intersection of [a54,b54],[a666,b666], etc.

so this original sequence of closed intervals also converges to [a,b]

Which is always nonempty, even if b=a.

QED?

Is this it? Just imagine that instead of shitty text I bothered to Tex it and that it looks beautiful

How does a thermistor work? I realise that resistance changes with temperature but what else changes due to Ohm's law, current or voltage?

>>8701806
It's essentially correct, although I don't know why it's asking you to use Bolzano-Weierstrass. The sequences an,bn are monotonic; the _entire_ sequence converges to a,b. This comes from the monotone convergence theorem which (as far as I'm aware) is strictly simpler than Bolzano-Weierstrass, since you need the former to prove the latter.

>>8701903
Thank you.

In this section it was talking about how all these theorems (monotone, cauchy, completeness, nested interval) are equivalent and is asking to prove them in every order.

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>>8701851
So the resistance of the thermistor changes with temperature.
With no information about the rest of the circuit, your question is pretty meaningless.

What I'd use to convert temperature into a usable reading (via a thermistor) is one of the most useful circuits out there: The voltage divider.
https://en.wikipedia.org/wiki/Voltage_divider

Lets say that our thermistor is Z2 and we use a reasonable sized resistor for Z1.

Then the voltage at Vout, which you could measure with a microcontroller or multimeter, would be
[eqn] V_{out} = \frac{Z2}{Z1 + Z2} V_{in} [/eqn]
The current going through the thermistor (and Z1) changes as well with temperature.

Back to your original question.
If you have a voltage source, and connected to either side of your thermistor, then yes the current going through the resistor would change with temperature (and of course your voltage source doesn't change, so the voltage across the thermistor would remain the same)

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anybody can help me, I was enjoying learning maths but every now and then these pop up and I fucking hate them

how the shit do I prove they're equal?

>>8701945
I just thought of something, do I have to use induction here?

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>>8701945
It is gonna come out rotated because phone, but de-rotate it.

Also, ignore top part. You interrupted my analysis to do this.

Why is this true?

Remember that n inside the sum is just a constant, so it "comes out"

And remember that the some of n times 1 is simply n

>>8701945
> that typesetting
triggered

>>8701953
You could.
Or you could just try manipulating it a bit.
make both start at k=0, then notice that n is a constant and pull 1/n^2 out of the sum.

>>8701981
I think the k=1 is a mistake. It must be.

>>8701979
>>8701981
>>8701983
thanks anons, you've saved my saturday

>>8701983
I see the 1+ in the second one and it makes me think they pulled out the monomial at least once.
But I haven't actually done the calculation, so I'd trust this guy >>8701979

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Can anyone explain this number sequence, I found it on an old hard drive and never figured out what it was.

>>8702017
That's just [math]\frac{3^x}{2^x}[/math] where X starts at 0
Also its in base 6

>>8702066
how the fuck did you figure that out?

>>8702066
nigga how did you know

>>8702070
All the digits were either 0,1,2,3,4 or 5 so I figured it's in base 6 so I converted it from base 6 to base 10. From there it was pretty obvious what it was.

>>8702080
niiiiiiigga

>>8702080
Alright that's reasonable, I thought of that after you posted the answer.

is sci a good place to ask research level question?

>>8700576
In the time it took you to make this post you could have typed it into a calculator or wolphram alpha.

But yes, your solution is correct.

>>8702190
dont ask to ask brainlet, just ask

Will my science get harder if I put more math into it?

>>8702310
I think what you mean is that you'll be able to do "harder" science if you put more math into it

is neural network the only big trendy thing on AI and machine learning now?

I've just started learning set theory, and I have a question about elementhood tests.

Say I want to write out the set of all integer squares. Which of these (are the multiple) is the correct way of doing it? Anything I shouldn't do? Like I'm a bit skeptical of this first one, I'm not sure whether you can only write the variable before the line, or if you can actually change stuff there, except including the universe.

1. [math]\{x^2 | x \in Z^+\}[/math]
2. [math]\{x | \sqrt{x} \in N\}[/math]
3. [math]\{x \in N | \sqrt{x} \in N\}[/math]

>>8702601

1 is fine

I see where you're going with 2 and 3, but they're more convoluted than 1, plus some people might quibble about the square root function not being injective i.e. you'd get negative numbers for the square roots which would not be in the naturals.

So for 2, no actual number satisfies it (unless you include 0 in the naturals) since they all have square roots < 0. Similar for 3. You could change their domain to the integers.

All that said, there are infinitely many ways to define a set, but some are simpler than others. 1 is the simplest choice.

>>8702637
>plus some people might quibble about the square root function not being injective i.e. you'd get negative numbers for the square roots which would not be in the naturals.
???
how is square root function not injective?

>>8702637
OK, thanks. I was just a bit confused about how to read the notation. I was using it a bit more like a regular equation, meaning if I wanted to see if 6 was in the first set, then I went:
6^2 = 36, welp, that's an integer! But obviously 6 shouldn't be in the set so it must be wrong.

But I'm supposed to go like this to test, right?
x^2 = 6, x ~= 2.45 which is not a positive integer, so it's not a member.

>>8702647

Well whatever the fuck the term is where a function maps onto multiple others. I'm getting at the fact that [math]sqrt{4} = 2, -2[/math] and -2 is not in the naturals. Therefore the definition number 2. cannot be satisfied.

>>8702660
do you not even know what a function is? functions don't have multiple outputs

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Guys p-p-please help.

Have to solve using integration by substitution. Can't check it on any online solvers, wont work.

>>8702662

I just used the term 'function' lazily. I was not aware that a function was only allowed to have one output for a specific input.

>>8702662
square root fucking relation then you fuckface i bet you're fun at parties

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>>8702666

Looks fine, anon

I am counting streaks that occur in financial data (consecutive positive increases or decreases). I want to know with what certainty a streak is likely to continue once it occurs and continues to occur. For example, one part of my data looks like streaks of
5: 84,
of 6: 52,
of 7: 28,
of 8: 11,
of 9: 5,
of 10: 2,
of 12: 2

Total 184 streaks.

So how do I tell with what confidence&probability (I dont really know the difference in this case and would like to know both) a streak of 5 will continue to 6, 6 to 7, etc. How can I get these estimates for streaks that didn't occur like of 11 or 13?

Thank you for your help!

>>8686591
>used in the treatment of autism

now i get why you want it so badly

lol

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>>8702722
>mfw I got it right
Thanks friend.

>>8688490
f(g(x+dx)) ~ f(g(x) + g'(x)dx) ~ f(g(x)) + f'(g(x))g'(x)dx

>>8693240
Still a weeb.

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Sup /sci
I'm trying to fix my education background and has been reading up some introductory texts on mathematics (e.g. Linear Algebra/ Calculus) while I'm free. Occasionally I would com across expressions like pic related.

My questions:
1. these kinds of expression means variables belong to a set of numbers, right?
2. Is there a guide/ branch of mathematic study that dictate the proper way of using such expression? I tried searching keywords like "mathematic expression" and "Real number set symbols" to no avail

>>8704109
Your pic says x is in the real numbers.

I had to go through this too once upon a time.
Best remedy is to read the introduction of a low level math text.
I think I used Hewitt - Real and Abstract Analysis

>>8704109
The first time I started learning about sets was with functions. It looks like your pic is saying the domain for a certain function is R.

>>8704169
>>8704287
Thanks

i want to illustrate the setup of my study

do i have go mspaint on that or are there programs to help out?

>>8704524
Corel Draw was the one that my lab used.

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lwhy does rape affect the humsn psyche so much?

>>8704529
Must have to do with the fact that having sex is tied to emotions, and also a very intimate thing.

Rape is not just "penis is vagina", it's forcing strong emotions into someone's brain, while violating their personal intimacy. If you add violence to this, the cocktail gets even stronger.

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Hey guys, a little unsure about part (a). Being above the x axis implies that the signed area is positive, but that's not really answering 'why'?
T-t-thanks g-g-guys.

>>8704658
if x > 1 then f(x) > 0

So that the points (x, f(x)) for x>1 are above the x-axis

>>8704666
I'm sorry but I don't understand how that explains it.

x = 0.5 gives x > 0.
Yet graph is below the axis for that value.

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anyone?

Hi guys, do you have any idea how can i estimate the value of the Charge density of a Capacitor ?

>>8704888
A point (x;y) is above the x-axis iff y > 0

>>8704893
Check if the axioms of vector spaces apply to solutions of the equations.
For example take two solutions u and v, and check wether u+v is also a solution.

>>8704903
But that isn't explaining why that happens? It's almost just restating the question in different words.
I thought it may be something to do with the properties of x^2 and lnx.

>>8704918
Just to add to what I mean.
For example, the graph of y =lnx is positive for all values greater than 1.

>>8704930
Just to add to this again. y = x^2lnx has the same x-intercept as y = lnx, which gives positive values for all inputs greater than 1. So I'm assuming the question wants an answer related to this.

>>8704943
Yes of course to find the sign of x^2 ln(x) you need the sign of x^2 and the sign of ln(x).

Don't you know about sign tables ?

>>8704950
I have used sign tables before, in differentiation for example. But I'm unsure as to how they are related to answering question (a).
Or are you saying that the reason why y = x^2lnx has positive values is because it contains y=lnx?

>>8704972
Positive values for x > 1**

>>8704903
right... so the solutions would only form a linear subspace if it was a straight line through (0,0)?
So does that mean solutions of D.E's never form linear subspaces?

>>8704978

x____ | 0____1_____
ln(x)__|___-__0__+
x2____|___+_____+
x2ln(x) |___-__0___+

How is that anywhere complicated ? You want the sign of a product, you build the sign table. You seem to be overthinking something.


>>8705019
Not a straight line, could be multidimentional. And of course some DE have linear subspaces (unsurprisingly, linear DE do).

>>8705030
ah yeah, i didnt consider higher orders...thanks for the help :)

>>8704658
So I've just thought of something related to part (a).

Since f(x) = x^2lnx is a product of h(x) = x^2 and g(x) = lnx, the domain of the new function is the intersection of the domain of f and g, which is why all values greater than 1 are positive.

Have I answered the question or am I on crack?

>>8705030
Quoting you since I just saw you posted again. Can you tell me your opinion on the above please.

>>8705048

> Since f(x) = x^2lnx is a product of h(x) = x^2 and g(x) = lnx,
ok

> the domain of the new function is the intersection of the domain of f and g,
ok, but why are you talking about the domain here ? What is your definition of domain ?

> which is why all values greater than 1 are positive.
wtf ??

>>8705056
The definition of domain we are using is "a set of allowed input values".

>>8705064
>The definition of domain we are using is "a set of allowed input values".

Ok, then what does it have to do with the output values ?

>>8705056
>> which is why all values greater than 1 are positive.
>wtf ??

All values above 1 in the domain of lnx are positive, since the domain of f(x) = x^2lnx is an intersection of the domains of lnx and x^2, the same must be true for the product of both.

>>8705073

Are you trying to say that
ln(x) > 0 for [math] x \in (1;+ \infty)
x^2 > 0 for [math] x \in (0;+ \infty)

and thus x^2ln(x) > 0 for [math] x \in (1;+ \infty) \cap (0;+ \infty) = (1;+ \infty) [/math]
or something like that ?

(we are then talking about the sets on which the functions are positive, not their domains).

The reasoning is correct, but in other situations it would become extra-convoluted (although that's somehow what we do when we build a sign table).

>>8705101

ln(x) > 0 for x ∈ (1;+∞)
x^2>0 for x ∈ (0;+∞)

and thus x^2ln(x) > 0 for x∈(1;+∞)∩(0;+∞)=(1;+∞)

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>>8705071
Because values greater than 1 in the domains of lnx and x^2 give only positive outputs. Since the domain of the product function f(x) =x^2lnx is an intersection of the domains of the individual functions x^2 and lnx, it must also give positive values for all inputs greater than 1. Or am I smoking crack?

>>8705111
the domain of ln(x) is (0; + ∞)
the domain of x^2 is (-∞; + ∞)

How do you get (1; + ∞) as an intersection of these ?

>>8684814

If a point is outside of a triangle in 3d will the area of the 3 triangles that are are made by drawing a line segment between the corners of the triangle and the point be greater than the original triangle's area?

Going to college soon. I really enjoy programming and math, but I've heard that CS degrees are memes. What do I choose, and why?

>>8705130
I'm not saying the domain is (1; + positive infinity) for f(x) = x^2lnx. It's (0; positive infinity) since it is an intersection of the domains of x^2 and lnx. Since lnx has (0; + positive infinity) as it's domain, the negative values of the domain of x^2 are not included in the product function f.

What I'm trying to say that is that both x^2 and lnx give positive outputs for all inputs in their domain that are x > 1. So the same is true for their product function f.

But I'm not sure. N-n-no bully please.

>>8704658
Consider [math]f(x)[/math] as a product of the functions [math]g(x)[/math] and [math]h(x)[/math]. [math]g(x) = x^2[/math] is very obviously positive for any [math]x \in \mathbb{R}[/math]. [math]h(x) = \ln(x) \geq 0[/math] for any [math]x \in [1,+\infty][/math]. The product of these two functions will therefore be positive for any [math]x\in[1,+\infty][/math].

At least, that's how I would go about it. Could be wrong.

Is there an easy way to get something like Wolfram|Alpha to plot graphs in the argand plane? I'm having trouble even getting it to do easy shit like g(t) = e^(it) with t in [0,1].

>>8705220
This is exactly what I was trying to say here.
>>8705185

Which cells produce growth factors? I've already looked online everywhere. All they talk about is the effects that growth factors have on cells. Where the fuck are they coming from? You'd think this would be a very important thing to note somewhere. The only one I know for sure is platelet-derived growth factor. The name gives it away.

>>8705185
> What I'm trying to say that is that both x^2 and lnx give positive outputs for all inputs in their domain that are x > 1. So the same is true for their product function f.

That's what I was asking here >>8705101


The reasoning is correct, but it's not an equivalence.
You have proven that f(x) > 0 for x ∈ (1;+∞), but you haven't proven that it is not for x ∈ (0;1]

>>8705236
lern 2 TeX nerd

>>8705251
I will s-s-senpai.

>>8705243
But don't you think they will accept that? I mean this is only A level math. I have never even been asked to do a proof yet.

What are some good books about potentiometric determination of inquinants in water?

>>8705270
I have no fucking idea, I don't even know what A level is. Just relax.

>>8705270
it doesnt even say "write a formal proof"
it's just "explain why"

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>>8705299
>>8705323
I'll go with that answer. Thanks guys.

>>8705237
Didnt hear of BDNF?
Anyway Id say almost all cells (eg during development) build at least some growth factors maybe except most matured like erythrocytes or acid producing cells in the stomach. What matters more is growth factor receptors, which are differentially expressed too.

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In a solar eclipse, what happen in the other side of world? absolute darkness?

f(x)= x^5+x^3+x

What is f(f^-1(5))?

If a sequence converges, does this imply the series converges? Getting mixed answers from my notes vs googlefu.

>>8705685
no

consider the constant sequence of 1s

>>8705632
5

[math]f(f ^{-1} (x)) \equiv x[/math] for any [math]f(x)[/math]

>>8705421
it's called night time

>>8705757
but without moon?

Could anyone maybe turn this into a formula that allows you to tweak the numbers a bit? I'm clearly not as math savvy as I thought I was and have no idea where to even start.

You have [10] batteries, and any amount of five types of appliances requiring [2], [3], [3], [4] and [4] batteries.

In how many combinations can you power up appliances using all batteries? I know for this instance it's 15 but I also want to know what would happen with 13 batteries or if one appliance used 6, and-so-on and it's getting a bit much to just keep manually doing it.

>>8705762
yes

>>8705777
https://en.wikipedia.org/wiki/Bin_packing_problem

"Suppose that log(a)2 = .90 and log(a)3 = 1.50
Evaluate the following:

a.) log(a)6
b.) log(a)8
c.) log(a)0.5
d.) log(a)1.5
e.) log(a)sqrt(3)

This was on a test where we weren't allowed to use calculators. Are you supposed to solve for a? I got a=cubedrt(9) by solving for a in log(a)3 = 1.50, but I didn't know where to go from there.

>>8706090
log(a)2 is log(base a)2
Not sure if I wrote that correctly

>>8706090
you're supposed to use the properties of logarithms, in particular the logarithms of powers...

>>8706246
Im not sure what you mean, using the properties of logarithms doesn't find the answer. And I'm not even sure what answer I'm supposed to be looking for if it's not a.

>>8706275
log_a(6) = log_a(3*2) = log_a(3) + log_a(2)
log_a(8) = log_a(2^3) = 3 * log_a(2)

and so on

is it possible for a positive function defined over the reals to have a finite integral over the domain??

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Why is the jew so prominent in science and math?


not anti semite just curious btw

>>8686591
10MG is 100$ on Sigma-Aldrich mate. You will be spending more learning how to do it by yourself and buying an apparatus.

>>8706446
https://en.wikipedia.org/wiki/Gaussian_integral