(本小题满分(13分),(Ⅰ)小问(6分),(Ⅱ)小问7分)
(Ⅰ)解:a1=S1=1,n≥2时,Sn=2-an,Sn-1=2-an-1,
∴an=?an+an?1?an=
an?1 (n≥2且n∈N*),1 2
∵a1=1,∴{an}是以1为首项,
为公比的等比数列,1 2
∴an=(
)n?1.…(6分)1 2
(Ⅱ)证明:bn=1+2log
bn=1+2log1 2
(1 2
)n?1=2n?1…(8分)1 2
令cn=
=1
bn?bn+1
=1 (2n?1)?(2n+1)
(1 2
?1 2n?1
),…(10分)1 2n+1
则Tn=
[(1?1 2
)+(1 3
?1 3
)+…+(1 5
?1 2n?1
)]1 2n+1
=
(1?1 2
)<1 2n+1
.…(13分)1 2