y=[cos^2(x)]^3+[sin^2(x)]^3=[cos^2(x)+sin^2(x)][cos^4(x)+sin^4(x)-cos^2(x)*sin^2(x)]立方和=cos^4(x)+sin^4(x)-cos^2(x)*sin^2(x)==[cos^2(x)+sin^2(x)]^2-2cos^2(x)*sin^2(x))-cos^2(x)*sin^2(x)=1-3cos^2(x)*...