Question

ДОКАЖИТЕ ТОЖДЕСТВО :

Answer 1

$frac{cos^2t}{1-sint}-sin^2t-cos^2t=frac{cos^2t}{1-sint}-(sin^2t+cos^2t)=frac{cos^2t}{1-sint}-1=\\=frac{cos^2t-(1-sint)}{1-sint}=frac{1-sin^2t-1+sint}{1-sint}=frac{-sin^2t+sint}{1-sint}=\\=frac{sint(1-sint)}{1-sint}=sint$