y=xarcsin(x/2)+√(4-x^2),y'=[xarcsin(x/2)]'+[√(4-x^2)]',=arcsin(x/2)+x*1/2*1/√(1-x^2/4)+1/2*(-2x)*1/√(4-x^2),=arcsin(x/2)+x/√(4-x^2)-x/√(4-x^2),=arcsin(x/2)解毕