13a1的知识精选

已知数列{an}是等差数列,a1=tan225°,a5=13a1,设Sn为数列{(-1)nan}的前n项和,则...
问题详情:已知数列{an}是等差数列,a1=tan225°,a5=13a1,设Sn为数列{(-1)nan}的前n项和,则S2014=()A.2014                              B.-2014 C.3021                    ...
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