Question

Упростите выражение:
(ctg^2α-cos^2α)(1/cos^2α-1)

Answer 1

$(ctg^2 alpha -cos^2 alpha )( frac{1}{cos^2 alpha } -1)=(ctg^2 alpha -cos^2 alpha )tg^2 alpha =\=ctg^2 alpha tg^2 alpha -cos^2 alpha tg^2 alpha=1-sin^2 alpha =cos^2 alpha$