Question

cos(180 ̊+a)cos(-a)/(sin(-a)sin(90 ̊+a)) упростить

Answer 1

$\frac{cos(180+\alpha)cos(-\alpha)}{sin(-\alpha)sin(90+\alpha)}=\frac{-cos\alpha \cdot cos\alpha}{-sin\alpha \cdot cos\alpha}=\frac{cos\alpha}{sin\alpha}=ctg\alpha$