Question

упростите cosa-1/sina * 1+cosa/sina

Answer 1

$\boxed{\; sin^2a+cos^2a=1\; \; \; \Rightarrow \; \; \; sin^2a=1-cos^2a}\\\\\\\frac{cosa-1}{sina}\cdot \frac{1+cosa}{sina}=\frac{cos^2a-1}{sin^2a}=-\frac{1-cos^2a}{sin^2a}=-\frac{sin^2a}{sin^2a}=-1$