17.(1)

·········································································· 4分
其振幅為

,相位為

,初相為

················································ 7分
(2) 可由

圖象橫坐標不變,縱坐標伸長到原來的

倍,再把曲線上所有的點向左平移

個單位,即可得

的圖象.································································· 9分
(3) 由

得

∵

∴

∴

∴

∴

·········································································· 13分