Một vật dao động điều hòa có đồ thị li độ theo thời gian như hình vẽ:

Pha ban đầu của dao động bằng:

\(x = 6cos\left( {\dfrac{\pi }{3}t - \dfrac{\pi }{3}} \right)cm\)

\(x = 6cos\left( {\dfrac{\pi }{3}t + \dfrac{\pi }{6}} \right)cm\)

\(x = 6cos\left( {\pi t - \dfrac{\pi }{6}} \right)cm\)

\(x = 6cos\left( {\dfrac{{2\pi }}{3}t - \dfrac{{5\pi }}{6}} \right)cm\)

\(\dfrac{\pi }{2} < \varphi < \pi \)

\( - \dfrac{\pi }{2} < \varphi < 0\)

\( - \pi < \varphi <  - \dfrac{\pi }{2}\)  

\(0 < \varphi < \dfrac{\pi }{2}\)

\({\rm{x}} = 16c{\rm{os}}\left( {2\pi t - \dfrac{\pi }{2}} \right)(cm)\)

\({\rm{x}} = 16c{\rm{os}}\left( {2\pi t + \dfrac{\pi }{2}} \right)(cm)\)

\({\rm{x}} = 8c{\rm{os}}\left( {2\pi t + \dfrac{\pi }{2}} \right)(cm)\)

\({\rm{x}} = 8c{\rm{os}}\left( {2\pi t - \dfrac{\pi }{2}} \right)(cm)\)

\(x = 2c{\rm{os}}\left( {\pi t - \dfrac{\pi }{2}} \right)cm\)

\(x = 4c{\rm{os}}\left( {2\pi t - \dfrac{\pi }{2}} \right)cm\)

\(x = 2c{\rm{os}}\left( {\pi t + \dfrac{\pi }{2}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\pi t - \dfrac{\pi }{2}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\dfrac{\pi }{3}t - \dfrac{\pi }{3}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\dfrac{\pi }{3}t + \dfrac{\pi }{6}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\pi t - \dfrac{\pi }{6}} \right)cm\)

\(x = 4c{\rm{os}}\left( {\dfrac{{2\pi }}{3}t - \dfrac{{5\pi }}{6}} \right)cm\)