1.x=π/4 则f(x)=sinπ/2 +2sin0 - 4cosπ/2 + 3cosπ =1+0-0-3=-22.x=3π/4 则f(x)=sinπ + 2sinπ/2 - 4cos3π/2 + 3cos3π/2 =0+2-0+0=2