Evaluating an integral without actually solving it
Is there any way to obtain the solution for the below integral without solving it?
Student X
Certainly. The function to be integrated is odd in nature.
If we let f(x)= x*e^|x|*sec x,
then f(-x) = (-x)*e^|-x|*sec (-x) = -x*e^|x|*sec x = -f(x)
This implies that the graph of f(x) has rotational symmetry about the origin. (A simple example would be the sine curve). Thus, if f(x) is integrated wrt x from -a to a for all a ∈ ℝ, then the result is simply zero.
Hope this helps. Peace.
Best Regards,
Mr Koh