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等差数列{an}的前n项的和为Sn,且a2013=S2013=2013,则a1=...
等差数列{an}的前n项的和为Sn,且a2013=S2013=2013,则a1=( )
A.2012
B.-2012
C.2011
D.-2011
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若α∈
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,tan(
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)=
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,则sinα=( )
A.
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B.
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C.-
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D.-
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若全集为实数集R,集合A={x|
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(2x-1)>0},则∁
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B.(1,+∞)
C.
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D.
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2),求a的取值范围.
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的值,若不存在,说明理由.
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