y=sin^4 x/4 + cos^4 x/4 y'=4sin^3(x/4)*cos(x/4)*(1/4)+4cos^3(x/4)*(-sinx/4)*(1/4)=sin^3(x/4)cos(x/4)-cos^3(x/3)sin(x/4)=sin(x/4)cos(x/4)[sin^2(x/4)-cos^2(x/4)]=(sinx/2)/2 * (-cosx/2)=(-sinx)/4y=(sin^4...