f(x)=sin2(x+y/2)
由于sin2x对称轴为π/4+kπ/2;
故x+y/2=π/4+kπ/2 x=π/4+kπ/2-y/2;
将x=x=π/8代入,得y=π/4+kπ,根据y的范围可知：y=-3π/4；