2023-07-25 19:45发布
因为tanα2,所以sin2α=2sinαcosα=2sinαcosα/(sin²α+cos²α)=2tanα/(1+tan²α)=4/5cos2α=cos²α-sin²α=(cos²α-sin²α)/(cos²α+sin²α)=(1-tan²α)/(1+tan²α)=-3/5
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因为tanα2,所以
sin2α=2sinαcosα
=2sinαcosα/(sin²α+cos²α)
=2tanα/(1+tan²α)
=4/5
cos2α=cos²α-sin²α
=(cos²α-sin²α)/(cos²α+sin²α)
=(1-tan²α)/(1+tan²α)
=-3/5
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