2siny-sin2y/2siny+sin2y упростить
(2siny-sin2y)/(2siny+sin2y) =
= (2siny - 2siny·cosy)/(2siny+2siny·cosy) =
= 2siny·( 1 - cosy)/(2siny·(1 + cosy)) =
= (1 - cosy)/(1 + cosy)