2) $$ \frac{cost}{1+sint} + \frac{cost}{1-sin^2t} =$$
$$ \frac{cost}{1+sint} + \frac{cost}{1-sin^2t} = \frac{cost}{1+sint} + \frac{cost}{(1-sint)(1+sint)} = $$
$$ = \frac{cost(1-sint)}{(1+sint)(1-sint)} + \frac{cost}{(1-sint)(1+sint)} =$$
$$=\frac{cost - costsint + cost}{(1+sint)(1-sint)} = \frac{2cost - costsint}{1-sin^2t} =$$
$$=\frac{cost(2-sint)}{cos^2t} = \frac{2-sint}{cost}$$
Ответ: $$ \frac{2-sint}{cost} $$