因为关于x=π/4对称
所以f(π/4-x)=g(π/4+x)
所以g（x）=f[π/4-(x-π/4]=f(π/2-x)
=2sin(π-2x+π/6)
=2sin(-2x+7π/6)
=-2sin(2x-7π/6)
=-2sin(2x+5π/6)