Question

упростите выражение cos2a/cosa-sin2a/sina

Answer 1

$frac{cos2 alpha }{cos alpha } - frac{sin2 alpha }{sin alpha } = frac{cos2 alpha cdot sin alpha -sin2 alpha cdot cos alpha }{cos alpha cdot sin alpha } = frac{sin( alpha -2 alpha )}{cos alpha cdot sin alpha } =- frac{1}{cos alpha }$