I wonder why
Since one are suppose to always submit the whole problem:
I didn't really manage to use your method but I called a friend and he said that curvelenght/area for always is equal to so I guess that I will just remeber that rule. But is that really true? What for
Moral, do not use rules you do not understand!
If f(x) is an even function, that is f(-x)= f(x), then , using the substitution u= -x.
So, again for an even function,
If f(x) is an odd function, that is f(-x)= -f(x), then , using the substitution u= -x.
Then, for an odd function, .
If f(x) is neither even nor odd, neither of those is true.