/sqt/: Stupid Questions Thread

No. Draw the normal line in, you'll notice that the angle made in air is larger than the angle made in vacuum. Remember snell's law, because the index of refraction in air is larger than the index of refraction in vacuum, the angle in air must be smaller than the angle in vacuum. You could draw any light ray from 8 to the moon, and you'll see that the angle in air is smaller than the angle in vacuum ONLY if the light ray is initially directed above the moon.

Just aim where you see it. Light from there is bend anyway so your light will go the same path.

x(t) = Acos(t)+Bsin(t)
y(t) = t + (B-A) cos(t) - (A+B) sin(t)

particular solution implies A = 0 and B=1

x(t) = sin(t)
y(t) = t + cos(t) - sin(t).

I got the general solution by differentiating the second equation and plugging in it the first one after that. This gives d2x/dt2 + x = 0
you get general form of x

then you replace in second equation to obtain directly general form of y.

Ah clever. I didn't think to differentiate to get rid of the y. Not that user btw.

>samefagging to make your answer look smart

Is this what these threads have become?

just trying to help, I couldn't care less about this.

>caring
Go cry about it, you wasted two full seconds of my life scrolling.

1/2

2/2

Where he got + 594/7 and -662/5?

Dude, I responded to your first thread with the answer and an explanation. If you didn't understand my post, why didn't you ask me a question? I'm not gonna ridicule you because this is a stupid questions thread after all, but let me give you a second shot at doing this thing yourself. Here's what I responded with:

Well if each clock's rate is constant (which they should fucking specify because this problem makes no sense anyway so they should be as specific as possible), then we know that 512-312 seconds on A is equivalent to 290-125 s on B. So we know the ratio A:B is 200:165. It tells us that A is 600 seconds, so we plug that into the equality
A/B=200/165
600/B=200/165
B=600*165/200=495 s
You can also make a ratio between B and C using 200-25 and 142-92, then use the 495 s we just calculated in this ratio to find what the time for C is.

The same procedure can be used for the next part of the problem, except instead of using 512-312 for A we use 512-400 for A and 290-x for B. Then you plug in A and B into that original ratio we found and solve for x.

its ratios:

40/33 s on clock A to 1 s on Clock B
3.5 s on Clock B to 1 s on Clock C
40/33 s on Clock A to 2/7 s on Clock C

, 600 s on Clock A = 990/7 s on Clock C
, 600 s on Clock A = (???-your turn)

,,,similarly, other parts follow

Is biological sex a social construct?

can anybody help me figure this stuff out?

its a differetial equation problem thanks

If you know the initial and final states of a system, and you also know the change of energy. Allegedly you can know if the change was due to work or heath transfer. How?

Also if an ice cube melts its volume changes. Is the change of its internal energy equal to the heath transferred? I'm guessing it has to be equal because energy goes from outside the ice to inside the ice, so it can't be bigger or lower, only equal right?

Can I get into a decent EE PhD with good/very good GREs, multiple papers (1st author on one, lower authorship on two others), but a 3.1-3.2 gpa? I never cared that much about grades because I assumed I'd go straight into industry, but I'm doing an internship at a research lab and it's making me reconsider.

The first law of thermodynamics is [math] q= \Delta E +W [/math] and work [math] W=P \Delta V [/math] so you're right if you know the initial volume and final volume, the pressure, and the change in energy you can determine the work done and using the first law determine the change in heat.

>Is the change of its internal energy equal to the heath transferred?
No, refer to the first law. The heat transferred is equal to the change in internal energy plus the work done ([math] P \Delta V [/math]). Also, in the case for phase changes, there is something called the latent heat which is apart of the total internal energy [math] \Delta E [/math] but does not contribute to a change in temperature, just change in phase.

How do you show that

So if the work in the ice example is negative, the change in internal energy would be bigger than the transferred heath? This means that I can just use the sign of the work to know which one of both is bigger?

where can i find good math articles? specifically linear algebra and applications.

I have absolutely no clue what to do here, we weren't taught this and there's no recommended reading material.

Write that transcendental functions are not real.

Short answer: probably.

But there's no surefire way to get into a PhD program unless you have connections in the faculty. Every admissions committee thinks different things are important and there's no telling beforehand how any given one will decide.

That said, publications are a massive boost when applying for a PhD. First and foremost they care if you can do research or not, and papers are a great signal that you can.

Can you not post joke responses?
People who can actually answer questions are more likely to notice posts with no replies.

>no fun allowed, just do my homework

idk for a

but for b) literally write out what cosh is in exponentials and do algebra

c) is a really really easy integral

[math]\pi = e^{\log(\pi)}[/math] and
[math]x = e^{\log(x)}[/math]

take it from there.

Just express cosh and sinh in their exponential form.

What happens to the Pollard ρ algorithm when it is run with n = 35, x1 = 6? Show that
the same thing happens (for at least one value of x1) whenever n = p(p + 2) for twin primes
p, p + 2.

please halp

If time passes more quickly the further we are from a center of gravity, does time stop when we're at the center of the earth?

>if it gets hotter the closer I get to the stove, does it reach an infinite temperature when I touch it
Of course not

everyone who posts after this line is gay
----------------------------------------------------------

Mom, dad, I need to tell you something

>Can you not post joke responses?
lmao reddit kid trying to moderate 4chyn threads

I'm a bit confused about combinations/exponential sets. I understand that combinations quite literally compute the number of combinations (irrespective of the order) of a number of elements out of a bigger set of elements.

But what do exponential sets compute? i.e. [math]N^{M}[/math]

the number of associations between two sets.
specifically:
if you start from a set A with M elements
and you go to a set B with N elements

then you can make N^M distinct functions that associate elements of A to elements of B : for each element on A, you can choose one of N elements of B. Do that M times, and you get N^M

What is the 'physical process' behind a hybrid initial velocity? Doesn't make sense to me

ah, that's my fault for not wanting to differentiate any of them. lol

Would something like this: ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-042j-mathematics-for-computer-science-fall-2010/index.htm

be useful for becoming a programmer or is this just useless baby math?

>we weren't taught this
What are the odds he means "my TA didn't do an example problem that looked just like this with different numbers :("

yes, but be careful, the change in internal energy can be negative, and so can the change in heat. So the sign of the work may not always tell you which of the two has a bigger magnitude.

ocw.mit.edu/courses/electrical-engineering-and-computer-science/6-042j-mathematics-for-computer-science-fall-2010/index.htm

Is this just useless baby math?

Could anyone tell me why this is wrong and can't be done, please? (self teaching hs math)

why is it that the closer I get away from being an animal and more human, the more expensive it gets? Fuck degrees.

The quadratic formula doesn't work on polynomials that have their x^2 coefficient greater than 1. You have to factor in a different way.

generally humans trade for more money than pets.

sorry mate we don't know what you're trying to do.

Probably not the right place to ask this, but there doesn't seem to be anywhere more appropriate.

I'm currently a comp sci/psychology double major with declared minors in biology, writing, and cognitive science. I'm most interested in biopsychology, cognitive psychology, and neural networking. Would it make sense to drop the bio minor for a math minor? From what I've heard, biology doesn't even help that much in biopsychology. I'd prefer not to drop the writing minor, but I'd be willing to if bio actually helped me with anything.

I'm gonna ask my psychology and my comp sci professors about this, but I'd like a little bit of user input. Thanks

What? The quadratic formula includes the leading coefficient.

Are there any reasonable researches proving superiority of diverse societies? Superiority defined as higher efficiency/productivity/lower crime-rate etc. not muh feelings inspirational bullshit.

There's research showing diversity in religious views leads to less trust and more conflict IIRC.

Tell me what to declare as my major, oh wise Veeky Forums. My biggest priorities are making a lot of money and working from home. I'm going to double major, btw.

>Electrical Engineering & Computer Science
Could do a wide range of jobs, seems very employable and likely to give me a type of job I could do from home. Could I ever go into grad school for math with this set up?

>Math and Computer Science
Probably a narrower set of jobs, but this would likely make me more qualified candidate for the jobs I CAN do from home.

I'm more interested in math and computer science, not actually really interested in hardware beyond trying to find an open source BIOS (for fuck sake) but I can't help but envision myself making boatloads of money by going into EE and CS and keeping math on the side.

I have until fall term to decide.

If we iterate by taking a convergent sequence and fitting it into each interval between its own points, then fitting it into the intervals between the points of that sequence and so on, can the limit of that process lead to different Hausdorff dimensions based on the sequence chosen?

Let set A={a,b,c}, B={d,e}

1)How many maps f:A->A satisfy f o f = f?

2) Can you find a pair of maps f: A->B, g: B->A for which g o f = 1_{A} (identity of A)

Need help with these..

Also for 2) If so how many such pairs.

I'd go for Math & CS. If you want to go to grad school for math you'll need more math than what you'll be exposed to with a CS degree.

1) seems f must be bijective, thus invertible. So f^{-1} exists. so f^{-1) f f = f^{-1} f, so f = identity.

2) No. the range of g can only contain at most 2 elements. thus g f can't be surjective.

sorry, this is wrong. rethinking...

Wrong, f can swap two elements.

I'm not set on grad school, but I'd like to keep that door open.

Which ones are most useful subjects/courses to actually study?.

single var calc, multivar calc, lin alg, math for cs, intro to CS and prog, introduction to algorithms

this shows that if the range of f is 3 elements, then f(a)=a, f(b)=b, and f(c)=c.

if the range of f is 1 element, there are 3 possibilities:
f(a)=f(b)=f(c)=a
f(a)=f(b)=f(c)=b
f(a)=f(b)=f(c)=c

So that's 4 maps so far, and you are left with the range being 2 elements.

f(a)=f(b)=a, f(c)=c works
f(a)=f(b)=b, f(c)=c works
f(a)=f(c)=a, f(b)=b works
f(a)=f(c)=c, f(b)=b works

f(a)=f(b)=c, f(c)=a doesn't work
f(a)=f(b)=c, f(c)=b doesn't work
no others

Looks like 8 total

thx user

Is there an oscillating function without imaginary numbers?

sin(x)
Re{sin(z)}

Most useless?

>without imaginary numbers

sin(x) doesn't have imaginary numbers in it. I know it's hard to believe.

Not that guy, but, while the result of sin(x) does not have imaginary numbers, an analytic expression of sin necessarily involves them. I believe is a fair complaint or at least note to make.

Mine is a little convoluted but I hope someone can figure it out, even within a rough estimate.

I have just "purchased" a home currently worth $500,000. I put $0 down when I did the deal. I currently owe $440,000 on the home. I will always be the only person paying the mortgage of lets say $1900 every month, and I will always have to split the equity 50/50 with my "investor" when I sell the property.

So being that there's $60,000 in equity in the home that at this moment technically ALL belongs to my investor, and I'm paying $1900 a month is there a point where I'll experience diminishing returns, where if I choose to keep the property and not sellI'll just be essentially paying for him to make more money and I'll stop benefiting from it? I'm assuming its the point when I've paid $30,000 into the mortgage (half the current equity) but I'm unsure.

How is consumer demand calculated?

>an analytic expression of sin necessarily involves them
no.
sin is just sin.
sin is a solution to y''+y = 0
sin(x) is the sum of the series (-1)^n * x^(2n+1)/(2n+1)!
If you think that somehow going through the exponential to define sin makes it more valid, think again.
So either the guy takes 30seconds to explain what he's really asking, or he won't get any valid answer.

I was just wondering why imaginary numbers are needed for rotations

Because real numbers are one-dimensional?

Science is a liar... sometimes.
So I'd spend less time doing that and more time earning God's graces.

Elaborate, please.

What would rotation mean on a line? You can multiply by -1 if you want. I must be misunderstanding your question.

Since we classify dogs differently based on their heritage (one breed is smarter/stupider/etc. than an other), is it ludicrous to apply that differentiation between interspecific organisms to humans?

(not a /pol/ shitposter, seriously just want to know)

What about for R^2?

You can accomplish rotation in R^2 with matrices. But R^2 is isomorphic to C, so it's in some sense equivalent to using i.

My personal analysis knowledge doesn't extend far enough to explain much further, hopefully that helps.

look at what -1 does: it takes a number on the real line and flips it a whole 180°. 5 becomes -5.
There is nothing in between.
Now imagine a number I that corresponds to a rotation of 90°.
That number would be such as I^2 corresponds to a rotation of 180°, or a negative number basically. If you want it to preserve length, you can also ask that I^2 = -1
and bam, you just got your first imaginary number: i.
If you want to go further to know what happens when you want other angles, watch this youtube.com/watch?v=oxF5VQSA4Hw

then you will also understand why e^(i*pi) = -1 is actually beautiful

What's the difference between R^2 and C?
thank you

With the binomial theorem, I don't understand how this part works.
It's clear that it's what gives the coefficients, but how?

C has multiplication and division defined.

Please answer.
Does it always fill up to Hausdorff dimension 1?

doesnt R2 also have multiplication define

>solve this while Veeky Forums is ded
>"you cannot delete a post this old"

scaling multiplication. C is pretty much R2 with complex number multiplication defined.

OP here:
f:A->B is many-to-one, g:B->A is one-to-many which violates the definition of a well-defined function, hence the inverses aren't functions. So, there is no such well-defined mapping.