Question

Упрастите выражение: 1-Sin2a*ctg2a

Answer 1

$1-sin2 alpha *ctg2 alpha =1-sin2 alpha * frac{cos2 alpha }{sin2 alpha } =1-cos2 alpha =cos^2 alpha +sin^2 alpha-$$(cos^2 alpha -sin^2 alpha )=cos^2 alpha +sin^2 alpha -cos^2 alpha +sin^2 alpha =2sin^2 alpha$