Never mind. I'll just right a short recursive function. It's easy
enough.
Alex
On Apr 23, 11:10 am, Alex Raichev <tortoise.s...@gmail.com> wrote:
> Hi all:
>
> Do any of you know how to get Sage to use the chain rule and expand
> the derivative of a composition involving one or two callable symbolic
> functions? Here's an example with one callable symbolic function.
>
> ----------------------------------------------------------------------
> | Sage Version 3.4, Release Date: 2009-03-11 |
> | Type notebook() for the GUI, and license() for information. |
> ----------------------------------------------------------------------
> sage: var('x,y,t')
> (x, y, t)
> sage: f= function('f',x,y)
> sage: g= exp(I*t)
> sage: diff(f(g,g^2),t).expand()
> diff(f(e^(I*t), e^(2*I*t)), t, 1)
>
> ------------------------------------------------------------------------
>
> The reason i ask is that i have to take higher-order derivatives of a
> composition f o g of two callable symbolic multivariate functions. I
> want the expanded form so that i can evaluate at a certain point c
> and solve a linear system to get the derivatives of f at g(c). (I
> know the values of the derivatives f o g and g at c.) I could write a
> Sage function to expand the derivatives of f o g using Faà di Bruno's
> formula, but before i do so, i was wondering if there's an easier
> way.
>
> Alex
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