17.(1)

·········································································· 4分
其振幅为

,相位为

,初相为

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

图象横坐标不变,纵坐标伸长到原来的

倍,再把曲线上所有的点向左平移

个单位,即可得

的图象.································································· 9分
(3) 由

得

∵

∴

∴

∴

∴

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