Докажите тождества: А)

Б) (sina/cosa) / (sina/cosa)+(cosa/sina)=sin^2a (sina/cosa) / (sin^2a+cos^2a) /sina*cosa)=sin^2a (sina/cosa) / (1/sina*cosa)=sin^2a sina*sina*cosa/cosa=sin^2a sin^2a=sin^2aA) cos^4a — sin^4a+2sin^2a / cos^2a=1/cos^2a cos^4a — sin^4a+2sin^2a=1 cos^4a — sin^4a+2sin^2a-sin^2a-cos^2a=0 cos^4a — sin^4a+sin^2a-cos^2a=0 (cos^4a-cos^2a) — (sin^4a-sin^2a)=0 -cos^2a (1-cos^2a)+sin^2a (1-sin^2a)=0 -cos^2a*sin^2a+sin^2a*cos^2a=0 0=0