f（x）=sin wx-cos wx
=√2（sinwx *cosπ/4-coswx * sinπ/4)
= √2sin(wx-π/4)
T=2π/w =π 带入得到 w=2
所以f（x）=√2sin(2x-π/4)
f（a/2)=√2sin(a-π/4)=1/3
所以 sin(a-π/4)=√2/6
后面的稍等一下哦 时间没了 谢啦