ASKSAGE: Sage Q&A Forum - RSS feedhttps://ask.sagemath.org/questions/Q&A Forum for SageenCopyright Sage, 2010. Some rights reserved under creative commons license.Mon, 24 Aug 2015 14:05:44 +0200How to define the derivative of a functionhttps://ask.sagemath.org/question/28796/how-to-define-the-derivative-of-a-function/ Hello,
I want to tell Sage what expression to use for the derivative of a funtion *a*. This vould be something like this: *diff(a,t) = b^2*. But this doesn't do the trick...
**Example**
I want to define this set of differential quations:
- aDot = da/dt = b^2,
- bdot = db/da = u.
I want Sage to find the relation between *a* and *u*. For that Sage needs to differentiate *a* twice:
- diff(a,t,2)
But to be able to calculate d^2/d *t* ^2 *a* = d/d*t *b*^2 = 2 *bu*, Sage needs to to both differential equations.
How can I implemant that?
Thanks alot in advance for your replies!
JohannesMon, 10 Aug 2015 07:03:28 +0200https://ask.sagemath.org/question/28796/how-to-define-the-derivative-of-a-function/Comment by niles for <p>Hello,</p>
<p>I want to tell Sage what expression to use for the derivative of a funtion <em>a</em>. This vould be something like this: <em>diff(a,t) = b^2</em>. But this doesn't do the trick...</p>
<p><strong>Example</strong>
I want to define this set of differential quations:</p>
<ul>
<li>aDot = da/dt = b^2,</li>
<li>bdot = db/da = u.</li>
</ul>
<p>I want Sage to find the relation between <em>a</em> and <em>u</em>. For that Sage needs to differentiate <em>a</em> twice:
- diff(a,t,2)
But to be able to calculate d^2/d <em>t</em> ^2 <em>a</em> = d/d<em>t *b</em>^2 = 2 <em>bu</em>, Sage needs to to both differential equations.</p>
<p>How can I implemant that?</p>
<p>Thanks alot in advance for your replies!</p>
<p>Johannes</p>
https://ask.sagemath.org/question/28796/how-to-define-the-derivative-of-a-function/?comment=29344#post-id-29344It sounds like the following might work for you: http://doc.sagemath.org/html/en/reference/calculus/sage/calculus/desolvers.html#sage.calculus.desolvers.desolve_systemMon, 24 Aug 2015 14:05:44 +0200https://ask.sagemath.org/question/28796/how-to-define-the-derivative-of-a-function/?comment=29344#post-id-29344