2020-01-07 17:44:42 +0200 received badge ● Notable Question (source) 2020-01-07 17:44:42 +0200 received badge ● Famous Question (source) 2018-04-16 11:45:46 +0200 received badge ● Popular Question (source) 2017-10-05 17:46:10 +0200 received badge ● Editor (source) 2017-10-04 18:52:26 +0200 received badge ● Student (source) 2017-10-04 18:52:23 +0200 received badge ● Self-Learner (source) 2017-10-04 18:52:23 +0200 received badge ● Teacher (source) 2017-10-04 18:48:52 +0200 commented question How to take partial derivative of abstract/unknown function? I found an example in the docs after asking: Solving Differential Equations Applying to the example given in the question though: var("x") f = function("f")(x) g = x * f g.diff(x)  Output: x*diff(f(x), x) + f(x)  2017-10-04 18:48:52 +0200 asked a question How to take partial derivative of abstract/unknown function? 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: var("x") f = ??? # how do I define this? g = x * f(x) g.diff(x)  Expected output: x * f'(x) + f(x)