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Differential Equations

- An equation involving derivatives of a function or functions. Solving ODE and PDE
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Jan16-12 Greg Bernhardt
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 30,176
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
95 138,508
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
3 730
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
0 722
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
1 602
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
5 666
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
2 549
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
3 768
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
3 736
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
10 926
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
2 573
Hi everyone, I just started to study Physics and I have a very simple question about integration. I'm blocked on...
Oct27-13 09:57 AM
Wonderland
14 596
I was taught that heat kernel can be used in any IBVP. However I don't understand "mathematically" how the image...
Oct27-13 05:14 AM
HAMJOOP
0 552
Hi, I'm somewhat new here, only posted a few times, and would like some help from you guys here if possible I'm...
Oct26-13 01:24 PM
hops1
18 1,584
Suppose ##f(x)=sinx,\quad 0<x<π##. Can you do a half-range sine expansion on f(x)? I tried, but I got...
Oct24-13 11:36 AM
ainster31
0 515
I want to compute the flux surfaces using FEM but i haven't found any good source to read. any help will be...
Oct24-13 09:22 AM
adwiteeymauri
2 786
I have an awful memory when it comes to factoids, I need to remember the Legendre, Hermite, Laguerre, Chebyshev,...
Oct23-13 05:16 AM
JJacquelin
2 696
Hi, The definition (see attachment) says that f(x) is a solution to the differential equation if it satisfies the...
Oct22-13 09:25 PM
BTP
1 791
Consider the PDE xu_x + yu_y = 4u. Suppose that we want to find the solution that satisfies u=1 on the circle x^2 +...
Oct22-13 09:35 AM
vanhees71
1 540
Hi, We can use Laplace transforms to solve DEs with these guys: ...
Oct22-13 04:18 AM
Uan
1 541
Hi, I am not sure if this is the correct forum, but... I am working with FFTs of real signals. I have a FFT of...
Oct21-13 11:13 PM
swraman
7 1,078
Hello all, I have boiled a very long physics problem down to the point that I need to solve the coupled equations ...
Oct21-13 09:50 AM
the_wolfman
6 799
can anyone direct me to a website that gives adequate treatment of the numerical solution of partial differential...
Oct21-13 08:43 AM
Chestermiller
1 589
Consider the following differential equations with initial conditions at time $t_0$ specified: \dot{x}_1 =...
Oct20-13 09:14 PM
Only a Mirage
0 418
Hello, Working through some reduction of order problems. I'm not sure about why the structure of a particular...
Oct19-13 09:04 PM
Simon Bridge
3 742
Good day. I was wondering if you could help me solve this first order linear partial differential equation: / = /...
Oct18-13 11:25 AM
berkeman
1 423
Something has been bothering me. I see a phrase like this: Plugging our two roots into the general form of the...
Oct17-13 02:44 PM
mesa
3 1,083
I ran into some formula: ^{a}_{0}∫J_{o}(kr) rdr= a/k J_{1}(ka) How can this be true? What property was used?
Oct16-13 08:22 PM
jasonRF
1 1,133
Helmholtz equation:##\nabla^2 u=-ku## is the same form of ##\nabla^2 u=f##. So is helmholtz equation a form of...
Oct16-13 06:09 PM
yungman
7 1,711
Hi, I'm trying to solve the flow profile inside an inhomogeneous porous material between two parallel moving plates...
Oct16-13 05:07 PM
Chestermiller
14 14,571
http://i.imgur.com/03izT8l.png Why is the math in the red box necessary? According to this definition, it isn't: ...
Oct16-13 04:42 PM
dextercioby
6 979
So, I'm trying to solve 2nd order linear differential equations (series solutions near a singular point). (lnx)y"...
Oct16-13 10:58 AM
Gridvvk
2 2,041
Hi all, If we have H'(r)=r+\tau(r)H(r) and \tau(r)=k+(H(r)/r)^a where
Oct16-13 08:31 AM
urbanist
2 598
I know nothing about DEs, so this may be a silly question. I'm given some time varying (x_t)_t and a constant r,...
Oct13-13 06:18 PM
economicsnerd
3 5,879
How can I determine the isotherms(curves of constant temperature) of given Temperature field like T = x^2 -y^2 + 8y....
Oct13-13 05:02 AM
mfb
5 5,014
When solving a differential equation for Bessel Functions, how do you know when to use the 1st kind or Neumann...
Oct13-13 04:30 AM
SteamKing
1 640
I need to prove that the solution of this differential equation: dx/dt = -x3 + 2*x + sin3(2*pi*t) - 2*sin(2*pi*t) +...
Oct12-13 12:31 PM
pasmith
1 1,369
For possion equation $$u_{xx}+u_{yy}=f$$ I know the general five point scheme is in the form...
Oct12-13 09:27 AM
AlephZero
1 827
When the rod is infinite or semi-infinite, I was taught to use Fourier transform. But I don't know when should the...
Oct12-13 06:00 AM
HAMJOOP
2 1,181
Consider the harmonic oscillator equation (with m=1), x''+bx'+kx=0 where b≥0 and k>0. Identify the regions in the...
Oct10-13 07:45 AM
jfizzix
1 1,404
Hello... My main problem is to find the Green's function of this pde:...
Oct10-13 04:29 AM
andreasgeo
0 797
Hello, I'm now working on a charge limiting system. I tried modeling it an easy way to be studied. ...
Oct9-13 05:37 PM
carb
4 2,534

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