# Differential Equations

- An equation involving derivatives of a function or functions. Solving ODE and PDE
 Views: 8,741 Announcement: Two free ways to get Gold Membership! Jan17-12 Meta Thread / Thread Starter Last Post Replies Views Please post any and all homework or other textbook-style problems in one of the Homework & Coursework Questions... Feb23-13 09:24 AM micromass 1 25,482 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 07:18 PM Luccas 95 120,108 Helmholtz equation stated that \nabla^2 u(r,\theta,\phi) =-ku(r,\theta,\phi) = f(r,\theta,\phi) This is being used... Nov21-13 02:12 PM yungman 0 633 Hi everybody, I need to solve a 1st order PDE for my thesis and I'm not a specialist in this field. I've read some... Nov20-13 06:36 PM Chestermiller 5 693 I have the following differential equation which I want to solve for y as a function of x ... Nov19-13 06:51 AM PSarkar 3 744 I am currently taking a course in PDE's and it has been very "applied" and not so much theory based. I can say its... Nov18-13 10:14 AM DeIdeal 4 720 Hello everybody, I have a small question related to multigrid. I am trying to solve a Poisson equation in 3D with... Nov18-13 05:04 AM kolmog 0 496 hey pf! here's the question: $$u \frac{ \partial u}{ \partial x} = \rho \frac{ d P}{ d x}$$ may i generally state... Nov18-13 01:45 AM joshmccraney 2 516 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 12:03 AM gikiian 4 673 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 02:40 PM lurflurf 5 634 Hi Fellows: If anyone has access to a copy of 'Differential Equations with Boundary-Value Problems (THIRD... Nov17-13 08:54 AM gikiian 2 682 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 08:11 AM drawar 2 511 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 04:01 PM yungman 0 468 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 06:05 AM SteamKing 8 781 hey pf! does anyone here have a link (or perhaps would care to share some info) on how to solve the biharmonic... Nov13-13 11:57 AM joshmccraney 2 585 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 07:39 AM HallsofIvy 3 888 The vector field F= looks exactly like the the direction field for the system dY/dt = {dx/dt = y} ... Nov11-13 07:33 AM HallsofIvy 1 485 The generalized Rodrigues formula is of the form K_n\frac{1}{w}(\frac{d}{dx})^n(wp^n) The constant K_n is... Nov9-13 11:13 PM bolbteppa 7 572 I have the following system of partial differential algebraic equations: \frac{1}{H_p}\frac{\partial H_p}{\partial... Nov6-13 04:55 PM ktsharp 2 612 Hello, I currently have a problem with interpreting how this statement was interpreted: We have a rate of change... Nov6-13 04:09 PM tiny-tim 3 589 Is there some systematic procedure to solve delay differential equation ? Here's one equation that I would like to... Nov6-13 03:23 PM pasmith 1 544 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 04:50 PM Rapier 0 517 Hello, I've been looking for the form of the solution(s) to following differential equations: ... Nov5-13 04:44 PM KrayzBlu 4 587 I have had this question on my mind for a long time When we solve a differential equation like this... Nov5-13 08:55 AM An1MuS 2 488 Consider the differential equation dx+ydy=0, the integration leads to (x2-x1)+(y2^2-y1^2)/2=0 (1) Suppose we... Nov5-13 07:58 AM JJacquelin 14 696 Hi there, I am trying to solve (analytically) a stochastic differential equation of the form: \frac{d^2}{dt^2}x... Nov5-13 04:55 AM fuchs 0 534 The point of my question is that when we divide a differential equation by a function or variable we result in... Nov4-13 11:40 AM inglezakis 0 420 Hi, i have to reduce the order of a 2nd order differential equation, to solve it with a numerical method. The... Nov4-13 09:45 AM vanhees71 4 494 I've got this far on a pde (second last step) but have no idea how they got this equality(I'm a noob), could someone... Nov3-13 07:54 PM Superposed_Cat 3 453 Hello there, I hope I'm posting in the right section. I have been doing some work on evolutionary game theory... Nov2-13 10:11 AM adam512 0 563 Differentiate the following with a positive index: \frac{2}{\sqrt{x}} What the book says: \frac{-2}{3x^... Nov2-13 08:19 AM noahsdev 3 438 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 01:41 AM Legaldose 2 556 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 12:04 PM Unredeemed 5 635 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... Oct31-13 11:11 PM vermin 3 569 Can someone help me code for the following? diffusion equation D∂^2/ ∂x=∂c/∂t D=diffusion coefficient =2*10^-4... Oct31-13 05:58 PM JWhite2013 0 536 I'm having difficulty in solving an exercise. http://imageshack.us/a/img542/484/765z.jpg They ask to reduce it... Oct31-13 11:23 AM MathematicalPhysicist 1 469 I just want to verify For Polar coordinates, ##r^2=x^2+y^2## and ##x=r\cos \theta##, ##y=r\sin\theta## ... Oct31-13 12:28 AM yungman 5 452 If ##r## is a function of ## x,y##, then \delta r= \frac{\partial r}{\partial x}\delta x + \frac{\partial r}{\partial... Oct29-13 06:57 PM yungman 2 398 Hi there, I'm trying to derive the following equation, but despite internet searching haven't been able to figure... Oct29-13 10:53 AM HallsofIvy 3 545 Google hasn't been very helpful on this one and my textbook once again assumes we are born with certain knowledge as... Oct28-13 11:20 AM Chestermiller 3 515 I am trying to solve this system DE's to determine the systems First Integral. dx/dt = y+x2-y2 dy/dt = -x-2xy I... Oct28-13 05:53 AM tiny-tim 10 641 Hi I am working on a project these days where I try to estimate the damping and spring stiffness. The way the physical... Oct27-13 11:35 AM SondreST 2 368