Question

cos²a-1/sin²a-1+ tg a cot a​

Answer 1

$\frac{Cos^{2}\alpha-1}{Sin^{2}\alpha-1}+tg\alpha*Ctg\alpha=\frac{-Sin^{2}\alpha}{-Cos^{2}\alpha}+1=tg^{2}\alpha+1=\frac{1}{Cos^{2}\alpha} \\\\Otvet:\boxed{\frac{1}{Cos^{2}\alpha}}$