f(x)*f(y)的导数是 f(x)的导数乘以f(y)+f(x)乘以f(y)的导数所以f(x)的导数是 1-(1/2*cos(x/2)*cos(x/2)+sin(x/2)*(-sin(x/2))*1/2)=1-(1/2*cos(x/2)^2-1/2sin(x/2)^2)=1-1/2(cos(x/2)^2-sin(x/2)^2) cosa^2-sina^2...