7
votes
Accepted
Symbolic solution for steady-state heat equation i.e. Laplace equation inside cylinder
This post contains several code blocks, you can copy them easily with the help of functions here.
It's not too surprising to see DSolve failing on the problem, ...
- 52.8k
6
votes
Accepted
How to achieve the transformation using DSolveChangeVariables introduced in Mathematica 13.1?
The problem can be solved with new-in-13.1 DSolveChangeVariables of course. If you read the document carefully, you'll notice the correct syntax should be
...
- 52.8k
6
votes
Analogue for Maple's dchange - change of variables in differential expressions
2022 Update: Included in Mathematica 13.1
As pointed out by xzczd in his question update, seven years later, finally Mathematica 13.1 introduced the new function DSolveChangeVariables which ...
- 414
5
votes
Accepted
5
votes
5
votes
How do I implement convolution integrals symbolically (not numerically)?
On second thought, I don't think your approach to calculating the convolution is mathematically sound. The Wiki page, and the MathWorld page it references, both state that "the integral of a ...
- 60.5k
4
votes
ComplexExpand no longer assumes Derivative[__][__][__] as real
Here another workaround that may be safe (as it would likely affect only expressions containing u'):
...
- 216k
4
votes
ComplexExpand no longer assumes Derivative[__][__][__] as real
Comments have identified this as a bug; in the meantime, a simple way to bring back the old behavior for ComplexExpand in a given session can be obtained by adding ...
- 8,208
4
votes
How do I implement convolution integrals symbolically (not numerically)?
s1[t_] := UnitBox[t - 0.5];
s2[t_] := SawtoothWave[t] UnitBox[t - 0.5]
res = Convolve[s1[s], s2[s], s, t]
$$\begin{array}{cc}
\{ &
\begin{array}{cc}
0.5 t^2 ...
- 16.2k
4
votes
Equating coefficients of two expressions
To be able to use "CoefficientList" we must first transform your equation to a polynomial by e.g. Lefthand Side-Righthand Side. Then we replace Cos[i theta] by e.g. c^i:
...
- 25k
3
votes
Equating coefficients of two expressions
Here's a way that's a bit silly but which should work. (I'm on a computer without MM on it right now, so if the code doesn't work please ping me in the comments and I'll fix it as soon as I'm able.)
<...
- 13.6k
1
vote
Loop over multiple variables with readable code
(I'm repeating some things I said in a comment just for the sake of completeness :) )
Welcome! In general, you shouldn't use For loops in mathematica, especially ...
- 8,208
1
vote
RSolve with integer and boolean variable
With the boundary conditions omitted, as permitted by @black, RSolve can solve this problem.
...
- 58.4k
Only top scored, non community-wiki answers of a minimum length are eligible