Question

Нужно срочно решить задание по алгебре

Answer 1

$sin^2\alpha +\frac{cos^2\alpha-1 }{sin^2\alpha-1} +cos^2\alpha =sin^2\alpha +cos^2\alpha +\frac{-(1-cos^2\alpha) }{-(1-sin^2\alpha)} =1+\frac{1-cos^2\alpha }{1-sin^2\alpha} =1+\frac{sin^2\alpha }{cos^2\alpha } =1+tg^2\alpha =\frac{1}{cos^2\alpha }$