BROS, PLEASEHELP ME SOLVE THIS TRIG PROBLEM !!!!!!!!!

HELLLLLLLLLLLLLLLLLP

>>728364777
i dont even know what language that is

0.447

>>728365255

TRIGONOMETRY

>>728365306
(B)

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I got this hold up OP I will not be cuck

>>728364777
NIGGER

>>728365255
>>728365336
literally before babby tier math.

I KNOPW IM SUPPOSED TO USE THE HALF ANGLE IDENTITY BUT I GET STUCK PUTTING (-3/5) INTO THE COS THETA PART

I DUNNO WTF TO DO HELLLLLLLP

(B) confirmed

>>728365545
Show me what you have so far

(cos(x) + 1)/2 = cos(x)²

If you can't do it with that then you're fucking bad

>>728365884
THE ANSWER SHEET SAYS IT IS D .. NOT B ... I DUNNO HOW TO DO THIS


>>728365940
OKAY ILL DO THAT

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that's literally basic math here in Brazil

>>728366215
That's not it, OP dealing with trigonometry

>>728366215
samefag

>>728366030
The only reason its - sqrt(5)/5 its because theta is between pi and -3pi/2

>>728366308

that's trigonometry

>>728366215

IT'S SUPPOSED TO BE NEGATIVE SQRT5/5

WRONG!!!!!!!!!!

>>728366501

read this >>728366400
dumbass

>>728366215
You retard, doesn't even know that the solution of x²=a are sqrt(a) AND -sqrt(a).

>>728366261
can't tell if you have alzheimer or autism. probably both.

>>728364777
Try wolfram alpha

>>728366596

how did you take cos(-3/5) and turn it into cos^angle/2 -sin^2angle/2?? ?

>>728364777
Can't be negative
Get Wolfram

>>728366817
Too lazy to write that

>>728366971
you can rewrite cos(theta) as cos(theta/2)² - sin(theta/2)²

The same way as cos(2theta) = cos(theta)² - sin(theta)²

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my progress so far............

what about theta/2 >pi/2 implies that sqrt((cos(theta) + 1)/2) = - cos(theta/2) ?

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>>728364777

>>728368271
Nice

>>728368271

can you please show how you do this algebraically ? I'm not supposed to be using a calc and i have no idea who julia is.

>>728368054
You can derive this just by using the pythagorean theorem. How old are you, fucking 12? jfc

>>728368718
should have specified non-calc in the OP, OP. give me a second

btw https://julialang.org/

btw if this thread goes of the end re-make it in /r/ or smth i'll find u

>>728364777

I solved it alread in /r/!
>>>/r/15339722

Greetings from Germany

>>728366817
why specify + and - if the quadrant the angle is in makes the whole thing negative?

>>728364777
use your half angle identity.

>>728364777
Cant you do arccos(-3/5) to find tetha in that range and then do cos(theta/2)?

>>728370645
how do you know x/2 is in quadrant 2 ?

>>728371450
see pic related, you can just approximate it visually

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>>728370645
Additional Informations!

>>728371450
Simple.
Omega is between pi and 3/2 pi. IF you divide it by 2, it will allways been greater than pi/2 and smaller than 3/4 pi. This is in quadrant II.

File: unit_circle_theta.png (210KB, 1024x1024px)

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>>728371726
whoops

>>728371726
thank you!!!! im stupid !!!!!

>>728371772
>>728371739
actually yeah cos should be on the other axis in mine
but you get the idea

>>728371772
hahaha i got the bounds wrong to in that pic

i'm such an idiot

pretend the green looks like a reverse D cause it should be pi to 3pi/2 not 0 to 3pi/2

>>728371772

Why is the result of cos(theta) on your y-axis?
cos(x) is allways on the x-axis.
sin(x) is located on the y-axis.

You missmatched sin and cos xD

>>728366261
At least you know to use the half angle identity.... But you dun fucked that all up.

It's cos theta, not cos(-3/5)

>>728372714
Should be square root of [1+(-3/5)]/2

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So this is what STEMlords do for fun...

I think I'll stick with saving the world, please.

(or rather, you're welcome)

>>728372987
Which is square root of (2/5)/2

Which is square root of 1/5

Which is D once you rationalize the denom...

>>728373031
stemlord here

>>728373031
so this is what non-stemlords post...

i think i'll stick with not shitting up boards with pictures from reddit

>>728373736
kek

>>728367482
I just want to point out you've mixed -4 and -3 on your little drawing.

>>728365513
>give me attention I'm smart I promise

>>728365372
retard

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>>728364777
only if u help me with my homework anon

>>728375853
Topology?

>>728376064
measure theory

>>728376100
Ur on ur own

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>>728376164
I'm actually just studying for the final exam rn, this was on an assignment lol so it's already done

>>728376312
Lewts.

I might take 1 class this summer. Not sure if they let me though.

>>728376312
Is this a graduate course? They don't offer this at the undergraduate level at my school (though I do go to a shitty state uni).

>>728377104
4th year undergraduate course. My uni is pretty rigorous in some cases; this is in the "pure math" department.

>>728377592
I'm doing pure math at mine but the highest we really go is analysis and modern algebra. I'm not even sure if topology is available to undergraduates here.

>>728378036
lol damn. my uni is considered best or 2nd best in Canada, so I don't know much about the US.
Analysis is pretty standard for undergraduate, and sometimes it includes basic elements of measure theory like Lebesgue measure and integration.

With that said, going to grad school with only analysis would be fine in most cases.

I'm going to Statistics master's so I need the measure theory for probability theory, since I'm focusing on stochastic processes and stochastic DEs

By what factor do you multiply to double the volume of a pie? Radius is 4cm but that's not enough?

It's cubic root but seriously how. I tried pluging numbers

>>728379488
I was curious as to if you were doing something statistics related, since, from what I've heard / read, theoretical probability is practically measure theory applied to the interval [0, 1]. I did a dual major in bio and pure math, with a minor in statistics. Not sure what I'm going to do with it yet kek

>>728380159
Bump

>>728380159
What is the formula for the volume of a pie lol

The answer is B.
cos-1(-3/5) = 126,8699
cos(126.8699/2) = 0,4472
0.4472 = square root of 5 / 5

>>728381550
I'm confused :c

I think it was cake. But how