3.
已知函数\(f(x)=2\sin (ωx+φ)(ω > 0,|φ| < \dfrac {π}{2})\)的图象过点\(B(0,- \sqrt {3})\),且在\(( \dfrac {π}{18}, \dfrac {π}{3})\)上单调,同时\(f(x)\)的图象向左平移\(π\)个单位之后与原来的图象重合,当\(x_{1},x_{2}∈(- \dfrac {4}{3}π,- \dfrac {2}{3}π)\),且\(x_{1}\neq x_{2}\)时,\(f(x_{1})=f(x_{2})\),则\(f(x_{1}+x_{2})=(\) \()\)