Question

Помогите Доказать тождество sin^2a-cos^2a-1/(cosa-sina)^2-1=cosa/sina

Answer 1

ctga=-2cos^2a/-2sina*cosa=cosa/sina=ctga

Answer 2

$frac{sin^2a-cos^2a-1}{(cosa-sina)^2-1}=frac{cosa}{sina}\\frac{-2cos^2a}{-2sinacosa}=frac{cosa}{sina}\\frac{cosa}{sina}=frac{cosa}{sina}$