Question

sin^2 a/1+ctg^2a(cos^2a-1) упростить

Answer 1

$frac{sin^2a}{1+ctg^2a}cdot (cos^2a-1)=frac{sin^2a}{frac{1}{sin^2a}}cdot (-sin^2a)=-sin^4acdot sin^2a=-sin^6a\\\star sin^2a+cos^2a=1; ; star \\star ; ; 1+ctg^2a=frac{1}{sin^2a}; ; star$