ASKSAGE: Sage Q&A Forum - Latest question feedhttp://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Sun, 20 Dec 2015 09:56:36 -0600Setting the conditions at t=0 for laplace transform with sage (instead of maxima)http://ask.sagemath.org/question/31713/setting-the-conditions-at-t0-for-laplace-transform-with-sage-instead-of-maxima/Hallo,
I am trying to calculate the laplace transform for the following differential equation with sage instead of maxima.
"m*'diff(x_f(t)+x_d(t),t,2)+d*'diff(x_d(t),t,1)+c*x_d(t)+Fext(t)=0"
But I do not find how to set the values in sage at t=0 for the functions x_d(t) and x_f(t). Before I did set it with maxima with
```
maxima.eval("atvalue(x_d(t), t=0, 0)$ atvalue('diff(x_d(t),t), t=0, 0)$");
maxima.eval("atvalue(x_f(t), t=0, 0)$ atvalue('diff(x_f(t),t), t=0, 0)$");
```
Basically, I am trying to use the sage laplace transfrom function instead of the sage-maxima function resulting in a nicer notebook without all the maxima.eval add maxima.-commands. I know that sage is using maxima for the transformation in the background.
BR Howil
howilSun, 20 Dec 2015 09:56:36 -0600http://ask.sagemath.org/question/31713/Problems with LaPlace transform when 'a' is negative in e^-athttp://ask.sagemath.org/question/8908/problems-with-laplace-transform-when-a-is-negative-in-e-at/ var('s t')
f = t^(-1)*exp(-t)-t^(-1)*exp((-3)*t)
f.laplace(t,s)
The above transform works as expected, however, when (-3) is changed to (3), I get the following error:
Traceback (click to the left of this block for traceback)
...
TypeError: ECL says: Maxima asks: Is s-3 positive, negative, or zero?
The Solution that I am expecting is:
log((s - 3)/(s + 1))
I don't know how to specify if s-3 is positive, negative, or zero. Any ideas?
Thanks,
Taylor Killian
tkillianThu, 19 Apr 2012 17:39:03 -0500http://ask.sagemath.org/question/8908/