Archived threads in /sci/ - Science & Math - 1762. page

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If statements A and B are true, how do we know that statements A and B are both true?

Is all logic just made up?

>inb4 classical logic is axiomatic

How do we know that we can suppose things?
For example, let's say I have an axiom that says A is true. I then suppose that if A is true, then B is true. Logically, B should be true.
Why? Because you've never seen or heard of a situation where given the statements "A is true" and "if A is true, B is true" in which B was not true? That doesn't mean there couldn't ever be one.

Note that this is different from saying "if A implies B and B implies C, then A implies C." That is axiomatic.

What I'm saying is "given A is true, and A implies B is true, how do we know that B is true?" This is, as far as I know, not specified axiomatically.

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Daily reminder that you never really produce energy, you only steal it.

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what will the next big breakthrough in chemistry be?

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Why are ice core data considered reliable?

If a warm period prevents ice formation or causes melting then past layers would mix and no new layers would form.

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Posted this on /adv/, but there aren't many academics that frequent that website.

So, /sci/, I've been incredibly lucky and incredibly blessed to have received two admissions offers to both Princeton's and Columbia's engineering MS programs with full financial support. I have to make a decision within the next few days, but I'm having a hard time choosing.

Columbia: I can transfer roughly half of the credits required for my degree program, finishing in about a year. During my graduate program (at whatever school I'm at), I want to take the opportunity to explore the theoretical side of my field more. Between the two schools, Columbia (says) that it offers more classes in this area, but it's somewhat unpredictable because the classes it claims to offer aren't always offered. I'm also quite familiar with professors at Columbia.

Princeton: I can't transfer any credits. The number of courses I have to take is similar, but there are more requirements in the way of TAing and doing a thesis, and I'd only be able to finish in 1.5 years if I severely push myself. According to the requirements, at least half of the courses will be spent taking analogs of courses I took during my undergrad, and the other half would be open to taking whatever variety I want (though the selection may possibly be more limited than at Columbia). Princeton's program has a better reputation (and ranking in my specific area of study).

Another confounding variable: I have two serious, competitive full-time offers at well-reputed and stable companies that will be there after my graduate program so long as I can start work in December of 2017. If I go to Columbia's program, I will certainly be able to finish in time, but if I go to Princeton's program, it will be a stretch, finishing within a week of having to start work.

What do, /sci/?

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Have I found the cheat code to nature?
Psychiatrist threw these at me after I scored a borderline positive on a verbal ADD test which asked questions like, "do you often get distracted."

I use them to study and my concentration is through the roof and suddenly I find boring things interesting. Is this feeling going to last?

Apparently if someone with real ADD takes them they have a different effect on their brain. But does that just mean if your a retard and you take stimulants, they boost you to the level of a normie, and if your a normie, they boost you to the level of superman?

>writing this on rit

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hey /sci/, I'm a bit of an hypochondriac, but I want some peace of mind on the subject.

how can I be sure I don't have a brain tumor?

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Is he right, /sci/? Will we see the Singularity in 2045 and be able to live forever, not work, and live with AI so smart that they solve all of humanity's problems? Part of me wants to believe and I do agree with some of his points, but once you listen to other scientists who disagree, it becomes harder to believe. What are your thoughts on Kurzweil and the Singularity?

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Hi all,

In my numerical analysis class we have been discussing lagrange and chebyshev interpolation

my professor derived a bound for the chebyshev interpolation [math] Q_nf(x) [/math] that is

[math] |Q_nf(x)| \leq ... \leq ||f||_{\infty} \int_0^{\pi} |\frac{\sin((n+1/2)\theta)}{2\sin(\theta /2)} | d\theta [/math] where [ math] \theta = \arccos x [/math]

they then conclude that [math] ||Q_n|| = \int_0^{\pi} |\frac{\sin((n+1/2)\theta)}{2\sin(\theta /2)} | d\theta [/math]

So my question is how do you make the jump

obviously we can take the sup over [math] Q_nf(x) [/math] to get [math] \frac{||Q_nf(x)||_{\infty}}{||f||_{\infty}} \leq \int_0^{\pi} |\frac{\sin((n+1/2)\theta)}{2\sin(\theta /2)} | d\theta [/math] but how do we get the final result about operator norm? seems more like we're bounding [math] ||Q_n|| [/math] instead of equating it

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>WHATS WRONG WITH MY CODE?

its a simple problem to invert the order of a vector (C language), but somehow the return values are totally wrong:

>#include <stdio.h>
#include <stdlib.h>
int main ()
{
int vet[3],i;
printf("give 3 numbers:");
for(i=0;i<3;i++){
scanf("%d",&vet[i]);
}
printf("\n reverse order is: \n");
for(i=2;i>=0;i--){
printf("%d ",&vet[i]);
}
return 0;
}

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I am looking for books about 1800-1900 era physics, that aren't 100% popsci - a little bit of actual physics would be nice!

Any reccs?

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<<<We're on the edge.

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Okay, so my retarded-ass college course isn't actually teaching me anything at all, it's all on computer and the book resource is useless. I have seen multiple people solve problems like this, and it isn't helping me solve THIS one. I only have one more chance to answer this problem before it locks me out, what the fuck do I do?

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Favorite fields of math?

CS major here, quite fond of algebra, combinatorics and graph theory.

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Hi /sci/, im working to reverse engineer this induction heater i got, and i think i have the right schematic (pic related).
Does this make sense? I find it particularly odd that the work coil doesn't seem to directly interact with the ground/negative terminal.

Those Schottky diodes are probably Schottky, they are model FR307. Feel free to assume that the values of all the components are reasonable.