2sin^2-1=0,7. Найти sin^4x-cos^4x
sin^4x-cos^4x=(sin^2x-cos^2x)*(sin^2x+cos^2x)= =(sin^2x-cos^2x)*1=sin^2x-cos^2x=sin^2x-(1-sin^2x)= =2sin^2x-1=-0,7