Question

Упростите выражение:
(tg a *ctg a-cos^2a)*1/sin^2a

Answer 1

(tga • ctga - cos²a)•1/sin²a = (1 - cos²a)/sin²a = sin²a/sin²a = 1.
(tga • ctga = 1; sin²a + cos²a = 1).