cos2a + 2sin(a+π\6) sin (a-π\6)

cos2a+2(sina*cos(п/6)+cosa*sin(п/6)*(sina*cos(п/6)-cosa*sin(п/6))=cos2a+2(sin^2(a)*cos^2(п/6)-cos^2(a)*sin^2(п/6))=cos2a+2(0.75*sin^2(a)-0.25*cos^2(a))=cos^2(a)-sin^2(a)+1.5*sin^2(a)-0.5*cos^2(a)=0.5(sin^2(a)+cos^2(a))=0.5как то так)