Question

Упростить выражение $\frac{2sin^{2} y-1}{2cos^{2} y-1} +cos^{2} y$

Answer 1

$\frac{2Sin^{2}y-1}{2Cos^{2}y-1 }+Cos^{2}y=\frac{-Cos2y}{Cos2y}+Cos^{2}y=-1+Cos^{2}y=Cos^{2}y-1=-Sin^{2}y\\\\Otvet:\boxed{-Sin^{2}y}$