Question

Даю 40 баллов за пример!!!

Answer 1

$2cos^2\alpha -1=cos2\alpha \\\\2sin\alpha \cdot cos\alpha =sin2\alpha \\\\4sin^2\alpha cos^2\alpha =(2sin\alpha \cdot cos\alpha )^2=sin^22\alpha$

$\frac{(2cos^2\alpha-1)}{4sin^2\alpha \cdot cos^2\alpha } -\frac{1}{sin^22\alpha } =\frac{(cos2\alpha)^2 }{sin^22\alpha }-\frac{1}{sin^22\alpha }=\frac{cos^22\alpha -1}{sin^22\alpha }=-\frac{sin^22\alpha }{sin^22\alpha } =-1$