3.
下面有五个命题,其中真命题的序号是_____________________.
\(①\)函数\(y = | \sin x|\) 的最小正周期是\(\pi \);
\(②\)终边在\(y\)轴上的角的集合是\(\{a|a=\dfrac{k\pi }{2},k\in Z}\);
\(③\)函数\(y=\cos (3x-\dfrac{\pi }{4})\)的对称中心为\(\left( \dfrac{π}{4}+ \dfrac{1}{3}kπ\right)(k∈Z) \)
\(④\)把函数\(y=3\sin 2x\)的图象向左平移\(\dfrac{\pi }{6}\)得到\(y=3\sin (2x+\dfrac{\pi }{3})\)的图象;
\(⑤\)函数\(y=\sin (x- \dfrac{π}{2}) \)在\(\left[0,π\right] \)上是减函数\(.\)