Question 139527
I think you have to prove that f(x) and f'(x)

integral from 0 to 1 of f(x)f'(x) is f(x)f(x)/2 evaluated
then integral from 0 to 1 of f(x)f'(x)= f(1)f(1)/2  - f(0)f(0)/2 = 0
then f and f' are orthogonal