Comparison of symbolic expressions
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Welcome.
A certain set of symbolic calculations is performed in two different ways. After that, you need to compare the results (we want them to be equal). But using " eq " or "= = " you can't get the desired result. You can use a trick and subtract or divide the results, but this method does not always work correctly.
Is there a function for comparing symbolic calculations?
Example:
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Answers (2)
KSSV
on 16 Feb 2021
syms a b
c = a+b ;
d = b+a ;
isequal(c,d)
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John D'Errico
on 16 Feb 2021
syms theta
isequal(sin(theta)^2 + cos(theta)^2,1)
Even worse, we see that while rewrite can seemingly improve this first counter-example, isequal still fails.
rewrite(sin(theta)^2 + cos(theta)^2,'sin')
isequal(rewrite(sin(theta)^2 + cos(theta)^2,'sin'),1)
The reason being that 1 and 1 are counter-intuitively not always seen to be equal, at least by isequal.
For this one, a carefully applied expand would have helped.
syms x
isequal((x+1)^3,x^3 + 3*x^2 + 3*x + 1)
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