[ducduyaktt]

let f be a function that the graph of f is semicircle with endpoints (a,0) and (b,0) where a<b ( a, b are real numbers)

18. The improper integral :[ integral(from a to b) f(x)f'(x)dx ] is necessarily ZERO.

Could anyone please explain it for me? Thanks


And ONE more question :

which letter is not homomorphic to letter C? J, N, S, O, U

Thanks so much