3sinx-√3cosx
=2√3(√3/2*sinx-1/2*cosx)
=2√3(sinxcosπ/6-cosxsinπ/6)
=2√3sin(x-π/6)
=2√3sin(x+b)
sin(x-π/6)=sin(x+b)
所以x-π/6=2kπ+x+b或x-π/6=2kπ+π-x-b
x-π/6=2kπ+x+b
-π/6=2kπ+b
b=-π/6-2kπ
所以k=0
b=-π/6
x-π/6=2kπ+π-x-b
这个不是恒等式
所以
b=-π/6