
Please post any and all homework or other textbookstyle problems in one of the Homework & Coursework Questions...

Feb2313 09:24 AM
micromass

1 
30,127 
My intent is to create a thread for people interested in Differential Equations. However, I will explicitly state that...

Jul312 07:18 PM
Luccas

95 
138,370 
If ##r## is a function of ## x,y##, then
\delta r= \frac{\partial r}{\partial x}\delta x + \frac{\partial r}{\partial...

Oct2913 06:57 PM
yungman

2 
548 
Hi there,
I'm trying to derive the following equation, but despite internet searching haven't been able to figure...

Oct2913 10:53 AM
HallsofIvy

3 
764 
Google hasn't been very helpful on this one and my textbook once again assumes we are born with certain knowledge as...

Oct2813 11:20 AM
Chestermiller

3 
734 
I am trying to solve this system DE's to determine the systems First Integral.
dx/dt = y+x2y2
dy/dt = x2xy
I...

Oct2813 05:53 AM
tinytim

10 
921 
Hi I am working on a project these days where I try to estimate the damping and spring stiffness. The way the physical...

Oct2713 11:35 AM
SondreST

2 
570 
Hi everyone,
I just started to study Physics and I have a very simple question about integration. I'm blocked on...

Oct2713 09:57 AM
Wonderland

14 
593 
I was taught that heat kernel can be used in any IBVP.
However I don't understand "mathematically" how the image...

Oct2713 05:14 AM
HAMJOOP

0 
551 
Hi,
I'm somewhat new here, only posted a few times, and would like some help from you guys here if possible
I'm...

Oct2613 01:24 PM
hops1

18 
1,577 
Suppose ##f(x)=sinx,\quad 0<x<π##.
Can you do a halfrange sine expansion on f(x)? I tried, but I got...

Oct2413 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...

Oct2413 09:22 AM
adwiteeymauri

2 
782 
I have an awful memory when it comes to factoids, I need to remember the Legendre, Hermite, Laguerre, Chebyshev,...

Oct2313 05:16 AM
JJacquelin

2 
692 
Hi,
The definition (see attachment) says that f(x) is a solution to
the differential equation if it satisfies the...

Oct2213 09:25 PM
BTP

1 
788 
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 +...

Oct2213 09:35 AM
vanhees71

1 
537 
Hi,
We can use Laplace transforms to solve DEs with these guys:
...

Oct2213 04:18 AM
Uan

1 
537 
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...

Oct2113 11:13 PM
swraman

7 
1,075 
Hello all,
I have boiled a very long physics problem down to the point that I need to solve the coupled equations
...

Oct2113 09:50 AM
the_wolfman

6 
792 
can anyone direct me to a website that gives adequate treatment of the numerical solution of partial differential...

Oct2113 08:43 AM
Chestermiller

1 
580 
Consider the following differential equations with initial conditions at time $t_0$ specified:
\dot{x}_1 =...

Oct2013 09:14 PM
Only a Mirage

0 
415 
Hello,
Working through some reduction of order problems. I'm not sure about why the structure of a particular...

Oct1913 09:04 PM
Simon Bridge

3 
740 
Good day. I was wondering if you could help me solve this first order linear partial differential equation:
/ = /...

Oct1813 11:25 AM
berkeman

1 
421 
Something has been bothering me. I see a phrase like this:
Plugging our two roots into the general form of the...

Oct1713 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?

Oct1613 08:22 PM
jasonRF

1 
1,130 
Helmholtz equation:##\nabla^2 u=ku## is the same form of ##\nabla^2 u=f##.
So is helmholtz equation a form of...

Oct1613 06:09 PM
yungman

7 
1,710 
Hi,
I'm trying to solve the flow profile inside an inhomogeneous porous material between two parallel moving plates...

Oct1613 05:07 PM
Chestermiller

14 
14,556 
http://i.imgur.com/03izT8l.png
Why is the math in the red box necessary? According to this definition, it isn't:
...

Oct1613 04:42 PM
dextercioby

6 
976 
So, I'm trying to solve 2nd order linear differential equations (series solutions near a singular point).
(lnx)y"...

Oct1613 10:58 AM
Gridvvk

2 
2,038 
Hi all,
If we have
H'(r)=r+\tau(r)H(r)
and
\tau(r)=k+(H(r)/r)^a
where

Oct1613 08:31 AM
urbanist

2 
595 
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,...

Oct1313 06:18 PM
economicsnerd

3 
5,876 
How can I determine the isotherms(curves of constant temperature) of given Temperature field like
T = x^2 y^2 + 8y....

Oct1313 05:02 AM
mfb

5 
5,004 
When solving a differential equation for Bessel Functions, how do you know when to use the 1st kind or Neumann...

Oct1313 04:30 AM
SteamKing

1 
638 
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) +...

Oct1213 12:31 PM
pasmith

1 
1,367 
For possion equation $$u_{xx}+u_{yy}=f$$
I know the general five point scheme is in the form...

Oct1213 09:27 AM
AlephZero

1 
823 
When the rod is infinite or semiinfinite, I was taught to use Fourier transform.
But I don't know when should the...

Oct1213 06:00 AM
HAMJOOP

2 
1,176 
Consider the harmonic oscillator equation (with m=1),
x''+bx'+kx=0
where b≥0 and k>0. Identify the regions in the...

Oct1013 07:45 AM
jfizzix

1 
1,395 
Hello... My main problem is to find the Green's function of this pde:...

Oct1013 04:29 AM
andreasgeo

0 
796 
Hello,
I'm now working on a charge limiting system. I tried modeling it an easy way to be studied.
...

Oct913 05:37 PM
carb

4 
2,534 
I'm finding for an example s.t.
$$Δu=f , 0≤x≤1, 0≤y≤\frac{\pi}{2}$$
$$Δu=0, x>1 , 0≤y≤\frac{\pi}{2}$$
let take...

Oct913 02:12 PM
sigh1342

0 
578 
I was wondering if there is a generalization of the following (roughly stated) theorem to ndimensional systems:
...

Oct713 03:35 PM
Only a Mirage

1 
2,022 
Hi all,
I'd be very happy if you could help me solve a problem in my research.
I need to prove the following:
...

Oct513 06:34 PM
pasmith

8 
8,174 
i got a book on differential equations that says a shortcut to solving the general differential equation...

Oct513 06:28 PM
fzero

1 
693 