Question

635. упростите выражение​

Answer 1

$\displaystyle\bf\\\frac{Cos^{2} \alpha }{Sin\alpha +1} =\frac{1-Sin^{2} \alpha }{Sin\alpha +1} =\frac{(1-Sin\alpha )(Sin\alpha +1)}{Sin\alpha +1}=1-Sin\alpha$