expand and simplify are not reverse?
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I thought any symbolic function that I expand I can simplify getting same results in both direction. But it seems to be just oneway, because:
syms z; simplify(expand(1/((z-1)*(z-i))))
does not give back
Walter Roberson on 9 Jul 2021
syms x t
simplify(sin(x)^2 + cos(x)^2)
simplify(2*(sin(t)^2 + cos(t)^2))
The first sin formula in x and the sin formula in t both simplify to 1 and the overall second expression simplifies to 2.
If it were true that expand() is the reverse of simplify then it follows that if you were to
then the result should be
sin(x)^2 + cos(x)^2 + 2 * (sin(t)^2 + cos(t)^2)
except that it should also be the same thing with several different variables instead. And, clearly, numerous other expressions.
We must arrive at the conclusion that expand() and simplify() are not inverse of each other.