12．（2023春•桐柏县校级月考）函数f(x)=cos(2x+φ)(0<φ<π)f(x)=\cos (2x+\varphi )(0<\varphi <\pi )f(x)=cos(2x+φ)(0<φ<π)的图象向左平移π6\frac{\pi }{6}6π个单位后与函数y=−cos2xy=-\cos 2xy=−cos2x的图象重合，则φ=\varphi =φ=___2π3\frac{2\pi }{3}32π___．