Seudónimo Seudónimo 04-05-2018 Mathematics contestada f(x) = cos(x) f'(x) = -sin(x) f'(π/2) = -sin(π/2) f'(π/2) = -1 My answer to this question is A. -1, but I am posting it here because several students got B. +1 as their answer. Can anyone confirm the answer as A?