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