f(x)=sin(wx+a)+cos(wx+a)
=根号下2sin(wx+a+π/4)
最小正周期=2π÷w=π w=2
f(x)=根号下2sin(2x+a+π/4)
f(x)=根号下2sin(2x+a+π/4)=根号下2sin(π/4+a-2x)
2x+a=π-(π/4+a-2x)
a=3π/8
f(x)=根号下2sin(2x+5π/8)
当2kπ-π/2