sin2x等于sin什么?
sin2x=2sinxcosx。
分析过程如下:
sin(α+β)=sinαcosβ+ sinβcosα
sin(α-β)=sinαcosβ-sinB*cosα
根据sin(α+β)=sinαcosβ+ sinβcosα可得:
sin2x=sin(x+x)=sinxcosx+sinxcosx=2sinxcosx
sin2x=2sinxcosx。
分析过程如下:
sin(α+β)=sinαcosβ+ sinβcosα
sin(α-β)=sinαcosβ-sinB*cosα
根据sin(α+β)=sinαcosβ+ sinβcosα可得:
sin2x=sin(x+x)=sinxcosx+sinxcosx=2sinxcosx
扩展资料:
二倍角公式
tan2α=2tanα/(1-tan^2(α))
cos2α=cos^2(α)-sin^2(α)=2cos^2(α)-1=1-2sin^2(α)
半角公式
sin^2(α/2)=(1-cosα)/2
cos^2(α/2)=(1+cosα)/2
tan^2(α/2)=(1-cosα)/(1+cosα)
tan(α/2)=sinα/(1+cosα)=(1-cosα)/sinα
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