Symbolically differentiation a function w.r.t a function
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How to differentiate 
with respect to 
; where, 
with the help of symbolic math tool. I tried writing
with respect to ; where, with the help of symbolic math tool. I tried writing syms f(x) g(x) h(x) x
g(x) = sqrt(f(x)^2 + x);
h(x) = diff(g(x),f(x));
but the following error pops up,
%Error using sym/diff (line 70)
%Second argument must be a variable or a nonnegative integer specifying the number of differentiations.
I am new to MATLAB and trying to understand the reason for this error and any suggestions on how can I write;
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Walter Roberson
2020-1-19
1 个投票
You cannot differentiate a function with respect to a different unknown function with normal calculus, because you cannot know that the functions are independent. You need Calculus of Variations to create operators for differentiating functions.
In the past I have posted examples demonstrating that the process suggested by Darova can generate the wrong answer.
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