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How to get correct partial derivatives using diff function?

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Robert  Flores
Robert Flores on 1 Oct 2019
Commented: Robert Flores on 1 Oct 2019
Hello,
I am trying to take the derivative of a logorithum that consists of three varibles, x1, x2, and u. I think the syntax of my code works somewhat okay, because I get part of the solution. However, I know it is wrong because I did it by hand, and I am missing some terms in the MatLab output. Below is a copy of my code so far. If anyone can help me resolve this issue, it will be greatly appreciated, thank you in advance.
I have attached a image of what the solution should look like. MATLAB_Question.PNG
Sincerely,
Robert
CODE:
clc, clear, close all
syms x1 x2 u
J = log(x1)+2*log(x2)+3*log(u);
% J = combine(J,'log','IgnoreAnalyticConstraints',true);
delJdelx1 = diff(J,x1)
delJdelx2 = diff(J,x2)

  2 Comments

Be Matlabi
Be Matlabi on 1 Oct 2019
In your hand written solution why haven't you cancelled out the common terms for example:-
Robert  Flores
Robert Flores on 1 Oct 2019
Oh my goodness, you are amazing. The script works then, haha, I have just been working out problems for to long. Thank you, haha

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