(Ⅰ)由题意得

························· 2分
因为cos
A≠0, ···························· 3分
所以tan
A="1." ····························· 4分
(Ⅱ)由(Ⅰ)知tan
A=1得

······················· 5分
=

························ 6分
=

····················· 7分
因为
x
R,所以

.······················ 8分
当

时,
f(
x)有最大值

,··················· 10分
当sin
x=-1时,
f(
x)有最小值-2,··················· 11分
所以所求函数
f(
x)的值域是

·················· 13分