Помогите найти производную

F (x) = sin x/3 - tg^2 (x)

F (x) = x-4 / √x^2-8

(√-корень)

F (x) = sin x/3 - tg^2 (x) F' (x) = cos (x/3) * 1/3-2tg (x)

F (x) = x-4 / √x^2-8 F' (x) = (u/v) '=1/v²[u'v-v'u]

u=x-4 u'=1 v=√x^2-8 v'=2x/2√x^2-8=x/√x^2-8

F' (x) = 1 / (x^2-8) [1*√ (x^2-8) - x * (x-4) / √x^2-8]