Question

Упростите sin^2a-1/cos^4a+tg^2a

Answer 1

$\displaystyle \frac{\sin^2\alpha-1}{\cos^4\alpha} +tg^2\alpha=-\frac{\cos^2\alpha}{\cos^4\alpha} -1+\frac{1}{\cos^2\alpha}=-\frac{1}{\cos^2\alpha}-1+\frac{1}{\cos^2\alpha} =-1$