Question

упростите выражение
cos2a/(cosa+sina)-cosa

Answer 1

$frac{cos2 alpha }{cos alpha +sin alpha } -cos alpha = frac{cos^2 alpha -sin^2 alpha }{cos alpha +sin alpha } -cos alpha =\= frac{(cos alpha+sin alpha )(cos alpha -sin alpha ) }{cos alpha +sin alpha } -cos alpha =cos alpha -sin alpha -cos alpha =-sin alpha$

Answer 2

спасибо