Question

упростите cosa-1/sina * 1+cosa/sina

Answer 1

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