Question

Помогите прошу! Упр 131, два первых примера

Answer 1

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

2)$frac{cos ^{2} alpha - frac{1}{ctg ^{2} alpha } }{cos alpha -sin alpha } = frac{cos ^{2} alpha - frac{1}{ frac{1}{sin ^{2} alpha } } }{cos alpha -sin alpha } = frac{cos ^{2} alpha -sin ^{2} pialpha }{cosa-sina} = frac{(cos alpha -sina)(cosa+sina)} {(cosa-sina)} =$ cosa+sina