Question

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

Answer 1

$(ctg^2 alpha +1)*sin^2 alpha -cos^2 alpha = frac{cos^2 alpha }{sin^2 alpha } *sin^2 alpha +1*sin^2 alpha -cos^2 alpha =$$cos^2 alpha +sin^2 alpha -cos^2 alpha =sin^2 alpha$