F(x)=ctg4x найти f'(x), f'(-Pi/6)

Question

F(x)=ctg4x найти f'(x), f'(-Pi/6)

Answer 1

f '(x) = (ctg4x)' = -4/sin²(4x)

f '(-π/6) = -4/sin²(-4π/6) = -4/sin²(2π/3) = -4/(3/4) = -16/3