Question

312(ә) вторую срочно...........

Answer 1

sin^4a (1-sin^2a)+cos^4a (1-cos^2a)=sin^2a*cos^2a
sin^4a*cos^2+cos^4a*sin^2a=sin^2a*cos^2a
sin^2a*cos^2 (sin^2a+cos^2a)=sin^2a*cos^2a
sin^2a*cos^2a=sin^2a*cos^2a