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How to take partial derivative of abstract/unknown function?

asked 2017-10-04 11:15:39 +0200

wrenoud gravatar image

I have a function f(x) that I do not want to be expanded but wish to evaluate the partial derivative of g(x,f(x),...) with respect to x, I can not figure out how to declare the function and indicate it is a function of x without an explicit definition.

Code example:

f = ??? # how do I define this?
g = x * f(x)

Expected output:

x * f'(x) + f(x)
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answered 2017-10-04 11:39:32 +0200

wrenoud gravatar image

updated 2017-10-05 17:46:10 +0200

I found an example in the docs after asking: Solving Differential Equations

Applying to the example given in the question though:

f = function("f")(x)
g = x * f


x*diff(f(x), x) + f(x)
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Asked: 2017-10-04 11:15:39 +0200

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Last updated: Oct 05 '17