# Differential Equations

- An equation involving derivatives of a function or functions. Solving ODE and PDE
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 Meta Thread / Thread Starter Last Post Replies Views Pinned: Intro. to Differential Equations ( 1 2 3 ... Last) My intent is to create a thread for people interested in Differential Equations. However, I will explicitly state that... Jul3-12 08:18 PM Luccas 95 117,363 Please post any and all homework or other textbook-style problems in one of the Homework & Coursework Questions... Feb23-13 10:24 AM micromass 1 24,585 Homework problem: For the wave equation: Utt-Uxx=0, t>0, xER u(x,0)= 1, |x|<1 Jul17-13 01:49 PM LCKurtz 1 578 Solve the difference equation yn+1=sqrt((n+3)/(n+1)) yn in terms of the initial value y0. y1=sqrt(3)y0... Jul14-13 06:13 PM HallsofIvy 1 393 Hi All, I need mathematical help from the topic electrical potential for lectures on physics by Richard Feynman. ... Jul22-13 01:33 PM SteamKing 10 677 Solve the difference equation yn+1=(n+1)/(n+2) yn in terms of the initial value y0. Jul21-13 09:00 AM HallsofIvy 11 665 Solve the difference equation yn+1=-0.9yn in terms of the initial value y0. y1=-0.9y0 y2=-0.9y1=(-0.9)2y0... Jul15-13 10:28 AM HallsofIvy 4 597 Ahoy! I'm trying to approximate f'(r) for the following equation using matched asymptotic expansions ... Jul26-13 06:31 AM pasmith 1 550 Hi, I derived the equation: 1+(y')^2-y y''-2y\left(1+(y')^2\right)^{3/2}=0 Letting y'=p and... Jul24-13 07:30 AM jackmell 5 576 Hello, I am new here. I hope I am posting my problem at the right place. I need some urgent help regarding the... Jul24-13 03:28 PM the_wolfman 1 425 Hi all, I'd like to solve the following problem in 3 dimensions: \partial_t u(r,t) = D\Delta u(r,t) u(r,0) = 0... Jul26-13 01:18 PM mfb 3 582 Is there a hole in knowledge as to the origins of PDEs? If there is a void, is Schwartz space a suitable basis? ... Jul25-13 09:02 PM MarneMath 7 624 The question of Solving a Pfaffian ODE can be interpreted as the question of finding the family of surfaces U = c... Jul27-13 08:51 AM bolbteppa 0 362 I would like to ask if anybody knows something about the methods of solving infinite linear autonomous systems of... Jul31-13 01:01 PM Mandelbroth 3 542 Hello all. I am working on a problem and I am getting a bit confused. Suppose we have a poisson equation that we... Jul30-13 05:46 PM freechus9 0 354 I am having this set of equations: ∂υ / ∂x + ∂v / ∂y = 0 u ∂υ / ∂x + v ∂u / ∂y = g ρ + κ ∂2u / ∂y2 u ∂T /... Aug1-13 01:51 PM MarioC 0 413 Hello All. I'm currently in a crash course on X-ray Diffraction and Scattering Theory, and I've reached a point... Aug1-13 03:16 AM SteamKing 7 532 Can I please get some help in understanding how Fourier developed his idea of heat transfer being a periodic phenomena? Aug13-13 12:52 PM HallsofIvy 5 567 I'm interested in solutions of an equation f'(x) = -\frac{xf(x)}{Af(x)+ Bx^2} with some positive initial... Aug12-13 09:42 PM jostpuur 13 524 Trying to make a calculation and I ran into the following diff equation: r''=a+b/r^2 And I can't seem to... Aug14-13 11:11 AM Galorian 3 435 Hi, hope this is a right place to ask this question. I work in the soil physics field and this problem has taken lots... Sep24-13 08:30 AM Chestermiller 3 369 Can someone help me code for the following? diffusion equation D∂^2/ ∂x=∂c/∂t D=diffusion coefficient =2*10^-4... Oct31-13 06:58 PM JWhite2013 0 374 Hi Fellows: If anyone has access to a copy of 'Differential Equations with Boundary-Value Problems (THIRD... Nov17-13 09:54 AM gikiian 2 521 Let y(t) = (y1(t), y2(t))^T and A(t) = (a(t) b(t) c(t) d(t)). A(t) is a 2x2 matrix with a,b,c,d all... Nov1-13 01:04 PM Unredeemed 5 505 Hello everyone, I'm having trouble understanding the solutions to DE's of the form: ay''+by'+cy=f(t) We've gone... Nov2-13 02:41 AM Legaldose 2 454 So, I have this DE which is 2nd order, w/ variable coefficients, it goes; xy''+(x-5)y'+(x^2-4)y=0 revolving around... Nov1-13 12:11 AM vermin 3 469 Differentiate the following with a positive index: \frac{2}{\sqrt{x}} What the book says: \frac{-2}{3x^... Nov2-13 09:19 AM noahsdev 3 365 Hello there, I hope I'm posting in the right section. I have been doing some work on evolutionary game theory... Nov2-13 11:11 AM adam512 0 423 Hello, I currently have a problem with interpreting how this statement was interpreted: We have a rate of change... Nov6-13 05:09 PM tiny-tim 3 491 Ok, so I start out with the basics and find k. F=ma=kx (1.5 kg)(9.8 m/s^2) = k (4.9 m) k = 3 N/m I also know... Nov5-13 05:50 PM Rapier 0 413 I have the following system of partial differential algebraic equations: \frac{1}{H_p}\frac{\partial H_p}{\partial... Nov6-13 05:55 PM ktsharp 2 497 Is there some systematic procedure to solve delay differential equation ? Here's one equation that I would like to... Nov6-13 04:23 PM pasmith 1 436 Hello - I asked a similar question before, but it was not resolved for me, and the person who answered was rude, so I... Nov11-13 08:39 AM HallsofIvy 3 785 The generalized Rodrigues formula is of the form K_n\frac{1}{w}(\frac{d}{dx})^n(wp^n) The constant K_n is... Nov10-13 12:13 AM bolbteppa 7 428 Given a function: z(x,y) = 2x +2y^2 Determine ∂x/∂y , Method 1: x = (z/2) - y^2 ∂x/∂y = -2y Method 2: Nov14-13 07:05 AM SteamKing 8 594 The vector field F= looks exactly like the the direction field for the system dY/dt = {dx/dt = y} ... Nov11-13 08:33 AM HallsofIvy 1 377 hey pf! does anyone here have a link (or perhaps would care to share some info) on how to solve the biharmonic... Nov13-13 12:57 PM joshmccraney 2 450 For ##\nabla^2 u(r,\theta, \phi)=0##, ##u(r,\theta, \phi)=r^{n}Y_{nm}(\theta,\phi)##. But I have issue with this,... Nov15-13 05:01 PM yungman 0 341 Let A be an 3x3 matrix such that A\mathbf{v_1}=\mathbf{v_1}+\mathbf{v_2}, A\mathbf{v_2}=\mathbf{v_2}+\mathbf{v_3},... Nov16-13 09:11 AM drawar 2 403 How do I find the second derivative of the function: f(x)= x^(2/3) (6-x)^(1/3) I have found the first... Nov17-13 03:40 PM lurflurf 5 489 If a_3(x)y'''+a_2(x) y''+a_1(x) y'+a_0(x)y=f(x) is an ODE with particular solution y_{p1} and a_3(x)y'''+a_2(x)... Nov18-13 01:03 AM gikiian 4 488 hey pf! here's the question: $$u \frac{ \partial u}{ \partial x} = \rho \frac{ d P}{ d x}$$ may i generally state... Nov18-13 02:45 AM joshmccraney 2 371

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