(tan x + cot x) cos 제곱 x =

(tan x + cot x) cos 제곱 x =

(tan x + cot x) cos & sup 2; x
= (sinx / cosx + cosx / sinx) cos & sup 2; x
= (1 / sinxcosx) cos & sup 2; x
= cosx / sinx
= cotx