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

Feb2313 09:24 AM
micromass

1 
29,630 
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 
136,780 
I know that the standard definition for a slope field is ##\frac{dy}{dx} = f(x, y)##, but and if the equation given is...

Apr1314 04:08 PM
HallsofIvy

1 
256 
f(x,y) = ln(9  x2  y2)
Domain I got:
(x, y) in R2 such that x2 + y2 < 9
How do I find the range from the...

Apr1214 12:09 PM
JC3187

6 
336 
Show that the explicit RungeKutta scheme
\begin{equation} \frac {y_{n+1} y_{n}}{h}= \frac{1}{2}
\end{equation}...

Apr1014 07:21 PM
rickyflair

2 
323 
If a system of firstorder ODEs like ##\frac{d\vec{r}}{dt}=A\vec{r}## have as solution ##\vec{r} = C_1 \exp(\lambda_1...

Apr1014 02:58 PM
Jhenrique

9 
527 
Hi All,
I am taking Dynamic Systems and Controls this semester for Mechanical Engineering. We are solving non...

Apr914 12:40 AM
MisterX

1 
365 
You can give me a good examples where ##\frac{\partial}{\partial x}## is different to ##\frac{d}{dx}## ?

Apr814 09:12 AM
Jhenrique

2 
358 
Hello
I am having some trouble understanding what the difference is between the reference solution and the "true"...

Apr714 07:36 AM
jjr

2 
423 
Hello guys, suppose we have an eigenvalue problem
\left\{
\begin{array}{ll}
u'' + λu = 0, ...

Apr214 10:44 AM
AlephZero

6 
499 
I realized that a PDE of 2nd order can written like: A:Hf+\vec{b}\cdot\vec{\nabla}f+cf=0
\begin{bmatrix} a_{11} &...

Apr114 09:22 PM
Jhenrique

0 
324 
Hi,
I am looking for a solution of
\frac{\partial\phi}{\partial t} =...

Apr114 06:50 AM
soni

0 
317 
Which the difference between diff equations of kind: \frac{dy}{dx} = \exp(x) \frac{dy}{dx} = 1/x
and diff equations...

Apr114 02:22 AM
Mark44

8 
383 
Hello, I have been trying to find an equation to represent the observed angular velocity of any object traveling in a...

Mar3114 08:50 PM
bendloewen

3 
403 
Hello,
I'm trying to analyze a system of elastically coupled oscillators, whose masses are all the same, using...

Mar3114 10:51 AM
Runei

1 
293 
Hello,
I am doing some physics and I end up with this PDE:
\frac{\partial q(x,y,t)}{\partial t} = (x^2 +...

Mar2814 02:51 PM
kosovtsov

4 
678 
How do we solve a system of coupled differential equations written below?
\frac{d^2}{dr^2}\left(
\begin{array}{c}...

Mar2714 11:04 PM
Ravi Mohan

2 
450 
Given a implicit ODE like F(x, y(x), y'(x), y''(x)) = 0, why your explicit form is y''(x) = f(x, y(x), y'(x))? Why a...

Mar2714 12:36 PM
micromass

4 
408 
If we have a constant coefficient second order homogeneous ODE, the way to solve this is to suppose a solution of the...

Mar2714 08:13 AM
quasar987

4 
368 
hello pf!
i am wondering if anyone here knows of a geometric, intuitive explanation for the laplace transform? if...

Mar2614 05:34 PM
micromass

3 
350 
I would like to learn this. Can someone teach me? The things like δy2/δ2x and solving for x and y. :rolleyes:

Mar2614 12:37 AM
z.js

10 
664 
I want to solve y''+y'+y=(sin(x))^2 and try to use
y=Ae^{ix} but then when I square it I get A^2 e^{2ix}
...

Mar2614 12:26 AM
lurflurf

1 
317 
Hi,
I know the weak form of the Poisson problem
\nabla^2 \phi = f
looks like
\int \nabla \phi \cdot...

Mar2514 01:12 PM
pasmith

1 
369 
It is very clear that the solution to the equation "dy/ya*dx/x = 0" is y=C*x^a. However I cannot figure out the...

Mar2414 05:27 PM
maajdl

5 
337 
Apparently it is a wellknown fact that if G(x)=(G_{ij}(x_1,\ldots,x_n)) is a smooth nxn matrixvalued function such...

Mar2014 03:04 PM
quasar987

0 
464 
px = t
t = s^2
$$ I = \int_0^∞ e^{s^2}ds$$
$$I*I = \int_0^∞ e^{s^2}ds * \int_0^∞ e^{u^2}du = \int_0^∞\int_0^∞...

Mar1914 03:11 PM
HallsofIvy

2 
457 
Hi, this question came up in my midterm and I was hoping to know if this is the correct method or answer.

Mar1814 04:18 PM
pasmith

5 
502 
Hello, I am learning about the general solution to higher order linear nonhomogeneous differential equations. I know...

Mar1714 11:59 PM
lurflurf

1 
391 
I am trying to work though an example on this topic in my book and have reached a point that I am not sure about. I...

Mar1714 04:00 PM
jellicorse

2 
341 
I've been playing around with the following system for the last little while:
(attached image: 2 Blocks +...

Mar1714 07:35 AM
aragorn77777

2 
421 
Hi there,
I am trying to solve a structural mechanics problem. I am doing so by two methods. On one hand, I am...

Mar1614 07:33 PM
c.teixeira

0 
337 
Hi,
I have been experimenting with FreeFem++, and have alos found a list of other free finite element packages.
...

Mar1614 10:09 AM
Morberticus

0 
318 
Hi everyone,
I have a question on the rate constant of a kinetic model(like the one we use in describing chemical...

Mar1314 07:50 PM
Chestermiller

3 
408 
How do you decide on the sign of a Hamiltonian function?
For example, I have the following system of differential...

Mar1314 09:21 AM
luitzen

0 
340 
Hi, it is easy solving these PDEs with the idealized homogeneous BCs they throw out in class, but I am having some...

Mar1214 08:49 PM
Chestermiller

9 
675 
Hello!
My goal here is to plot the solution to the bioheat equation for a tumor as a function of time. I'm plotting...

Mar1214 04:08 PM
Chestermiller

9 
498 
Hello,
As of recently, I've been working with Laplace transforms and have a question about their relationship to...

Mar1114 09:58 AM
the_wolfman

6 
733 
Hello, does anyone knows the Integral of (dx)^2
Excuse my english, I hope I had make myself clear, thanks

Mar814 07:08 PM
micromass

6 
563 
I was wondering if somebody could clear up some confusion I have regarding this.
I've been going over the...

Mar814 06:56 AM
jellicorse

2 
337 
Hello,Iam facing a problem with using FindMinimum Function .Can any body help me ?
First I used FindRoot fuction to...

Mar814 03:45 AM
Reem Hashem

0 
282 
Notice that, when solving secondorder linear homogeneous constantcoefficient ODEs, the classic linearly independent...

Mar614 02:18 PM
lurflurf

1 
400 
By a fortuitous mistake in copy/pasting, I happened across this system. It exhibits very chaotic behavior for some...

Mar614 08:40 AM
TylerH

1 
356 