f(x)=(1/2)sin2x－(1/2)cos2x＋(1/2)=(√2/2)sin(2x－π/4)＋(1/2).1、代入计算,f(π/4)=1/2；2、x在[0,π/2],则2x－π/4在[－π/4,3π/4],最大是f(3π/8)=√2/2＋1/2,最小是f(0)=0.