等差数列{an}中,a2+a7+a15=12,则a8= .
考点分析:
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或
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4x-sin
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D.函数
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的图象是关于点
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设函数f(x)=x-2sinx是区间[t,t+
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]上的增函数,则实数t的取值范围是( )
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