真是的撒旦撒旦撒旦撒旦爱的淡淡地
(1)
Sn= 2an -2
n=1 , a1= 2
an = Sn-S(n-1)
=2an -2a(n-1)
an = 2a(n-1)
= 2^(n-1) .a1
= 2^n
点P(bn，b(n+1) )（n∈N*）在直线y=x+2上
b(n+1) = bn+2
b(n+1) -bn =2
bn -b1 = 2(n-1)
bn = 2n-1
(2)
cn =an. sin2nπ -bncos2nπ ????????
请清楚题目！
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