sin(x)^6+cos(x)^6 ＝[sin(x)^2+cos(x)^2]*[sin(x)^4-sin(x)^2*cos(x)^2+cos(x)^4] ＝sin(x)^4+2*sin(x)^2*cos(x)^2+cos(x)^4-3*sin(x)^2*cos(x)^2 ＝[sin(x)^2+cos(x)^2]^2-3*sin(x)^2*cos(x)^2 =1-3*sin(x)^2*cos(x)^2 =5/8+3/8*cos(4*x)