2sin(x-π/4）sin(x+π/4)
=2sin(x-π/4)cos[π/2-(x-π/4)]
=2sin(x-π/4) cos(π/4-x)
=2sin(x-π/4) cos(x-π/4)
=sin(2x-π/2)
=-sin(π/2-2x)
=-cos2x
∴ f(x)=cos2xcosπ/3+sin2xsinπ/3-cos2x
=-(cos2xcosπ/3-sin2xsinπ/3)
=-cos(2x+π/3)
T=2π/2=π
对称轴2x+π/3=kπ
x=（kπ-π/3）/2
做到这一步,相信下面的你会做了,不懂再问我.
建议楼主多给点分,还有你的三角函数要好好的学习,高考肯定是免不了的