Question

Решить: $\frac{cos\alpha }{1+sin\alpha } +\frac{cos\alpha }{1-sin\alpha }$

Answer 1

$\frac{cosa}{1+sina}+\frac{cosa}{1-sina}=\frac{cosa*(1-sina)+cosa(1+sina)}{1-sin^2a}=\frac{cosa(1-sina+1+sina)}{cos^2a}=\\\\=\frac{2}{cosa}$