 # Obnoxious

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• Birthday 03/14/1989

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## Obnoxious's Achievements 10

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1. ## Ordinary differential equations question

Okay, so basically, I have to actually work out the expression and solve for r? $-Ar^2\sin(rt+b) + K_1Ar\cos(rt+b) + K_2A\sin(rt + b) = 0$ as in expand the thing with trig identities and mush out an answer? There's no easy way?
2. ## Ordinary differential equations question

In the equation: $\frac{d^2x}{dt^2} + K_1\frac{dx}{dt} + K_0x = 0$ Can someone please explain to me how I'm suppose to be able to use the trig answer $x=A\sin(rt + b)$ or $x=A\cos(rt + b)$ to get to the characteristic equation? Everytime I try to mush the equations around I get stuck at this junction: $-r^2x + K_1Ar\cos(rt + b) + K_0x = 0$ or $-r^2x - K_1Ar\sin(rt + b) + K_0x = 0$ I seriously need some help on this as I'm learning this stuff on my own, and therefore have no professor to turn to with questions.
3. ## What exactly is "sum over path?"

I read about Richard Feynman's theory of sum over path in a book early this year, but I still don't exactly understand it - just how does he assign numbers to each different path an object could take and cancel out all but one path?
4. I'm still in high school, so I get to take community college courses (namely at East Los Angles Community College and Pasadena Community College) for free (w00t California)!!
5. Oh well, I guess it's about time I find myself a job...Oh well, at least I could still take community college courses for free.
6. Damn this price of education!! What happened to American socialism?!?!
8. Not the London one.
9. Can someone please explain to me how it was derived that gravitons travel at the speed of light?
10. Is Ozone polarized?
11. as in angular momentum = displacement vector x linear momentum Can someone please explain to me what the displacement vector is? I tried looking on wiki, but to no avail.
12. Can someone help me find the volume of a torus? I understand how to find volume with the integral, but the torus is giving me sufficient trouble. Worse yet, the calculus teacher at my school refuses to answer my questions because I'm not in his calculus class.
13. Yeah, that's what I meant, thanks!
14. No, I mean f of a real number is another real number. But I have no idea how to make the funky looking R with Latex
15. Is the set of functions: {$f® = R |\frac{df}{dx} + 2f = 1$} a vector space? I said no because it doesn't seem to have a zero vector, but I'm doubtful of my answer. Can someone help me prove its vector space validity (or lack thereof)?
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