化简化简[2(cosα)^2-1]/2tan[(π/4)-α]sin[(π/4)+α],急用啊

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化简化简[2(cosα)^2-1]/2tan[(π/4)-α]sin[(π/4)+α],急用啊

化简化简[2(cosα)^2-1]/2tan[(π/4)-α]sin[(π/4)+α],急用啊
化简化简[2(cosα)^2-1]/2tan[(π/4)-α]sin[(π/4)+α],急用啊

化简化简[2(cosα)^2-1]/2tan[(π/4)-α]sin[(π/4)+α],急用啊
[2(cosα)^2-1]=cos2α
tan[(π/4)-α]=sin[(π/4)-α]/cos[(π/4)-α]
cos[(π/4)-α]=sin[(π/4)+α] sin[(π/4)-α]=cos[(π/4)+α]
所以
2tan[(π/4)-α]sin[(π/4)+α]=sin[(π/4)-α]
[2(cosα)^2-1]/2tan[(π/4)-α]sin[(π/4)+α]=cos2α/sin[(π/4)-α]
也可化简为cotα*cos[(π/4)-α]
cotα*sin[(π/4)+α]
用到的三角函数公式:
cos(α+β)=cosαcosβ-sinαsinβ
cos(α-β)=cosαcosβ+sinαsinβ
sin(α+β)=sinαcosβ+cosαsinβ
sin(α-β)=sinαcosβ -cosαsinβ
sin2A=2sinA·cosA
1.Cos2a=Cos^2(a)-Sin^2(a)
2.Cos2a=1-2Sin^2(a)
3.Cos2a=2Cos^2(a)-1
tanα=sinα/cosα

(2cosα^2-1/cosα^2+tanα^2)/(2tan(π/4-α)sin(π/4+α)^2 =(2cosα^2-1-tanα^2+tanα^2)/(2*sin(π/4-α)*sin(π/4+α)