Question

упростите выражение:
а) cos 2 a/cos a-sin a
б)cos2 B+sin^2 B
в)sin B/2 cos^2 B/2

Answer 1

а)
$frac{cos2 alpha }{cos alpha -sin alpha } = frac{cos^2 alpha -sin^2 alpha }{cos alpha -sin alpha } = frac{(cos alpha -sin alpha )(cos alpha +sin alpha )}{(cos alpha -sin alpha )} =cos alpha +sin alpha$
б)
$cos2 beta +sin^2 beta =cos^2 beta -sin ^2beta +sin^2 beta =cos^2 beta$