已知tanα＝-3分之1 求2sinαcosα+c - 知识问答

已知tanα＝-3分之1 求2sinαcosα+cos²α分之1

3个回答

tanα=2/3
1/(sinαcosα)
=2/(2sinαcosα)
=2/sin(2α)
=2/(2tanα/(1+(tanα)^2))
=(1+(tanα)^2)/tanα
=(1+(2/3)^2)/(2/3)
=(13/9)/(2/3)
=13/6

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