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sinα=tanαÃcosα
cosα=cotαÃsinα
tanα=sinαÃsecα
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secα=tanαÃcscα
cscα=secαÃcotα
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cos(α+β)=cosα·cosβ-sinα·sinβ
cos(α-β)=cosα·cosβ+sinα·sinβ
sin(α±β)=sinα·cosβ±cosα·sinβ
tan(α+β)=(tanα+tanβ)/(1-tanα·tanβ)
tan(α-β)=(tanα-tanβ)/(1+tanα·tanβ)
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sin(α+β+γ)=sinα·cosβ·cosγ+cosα·sinβ·cosγ+cosα·cosβ·sinγ-sinα·sinβ·sinγ
cos(α+β+γ)=cosα·cosβ·cosγ-cosα·sinβ·sinγ-sinα·cosβ·sinγ-sinα·sinβ·cosγ
tan(α+β+γ)=(tanα+tanβ+tanγ-tanα·tanβ·tanγ)/(1-tanα·tanβ-tanβ·tanγ-tanγ·tanα)
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Asinα+Bcosα=(A�0�5+B�0�5)^(1/2)sin(α+t)ï¼å
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sint=B/(A�0�5+B�0�5)^(1/2)
cost=A/(A�0�5+B�0�5)^(1/2)
tant=B/A
Asinα-Bcosα=(A�0�5+B�0�5)^(1/2)cos(α-t)ï¼tant=A/B
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sin(2α)=2sinα·cosα=2/(tanα+cotα)
cos(2α)=cos�0�5(α)-sin�0�5(α)=2cos�0�5(α)-1=1-2sin�0�5(α)
tan(2α)=2tanα/[1-tan�0�5(α)]
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sin(3α)=3sinα-4sin�0�6(α)=4sinα·sin(60+α)sin(60-α)
cos(3α)=4cos�0�6(α)-3cosα=4cosα·cos(60+α)cos(60-α)
tan(3α)=tan a · tan(Ï/3+a)· tan(Ï/3-a)
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sin(α/2)=±â((1-cosα)/2)
cos(α/2)=±â((1+cosα)/2)
tan(α/2)=±â((1-cosα)/(1+cosα))=sinα/(1+cosα)=(1-cosα)/sinα
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sin�0�5(α)=(1-cos(2α))/2=versin(2α)/2
cos�0�5(α)=(1+cos(2α))/2=covers(2α)/2
tan�0�5(α)=(1-cos(2α))/(1+cos(2α))
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sinα=2tan(α/2)/[1+tan�0�5(α/2)]
cosα=[1-tan�0�5(α/2)]/[1+tan�0�5(α/2)]
tanα=2tan(α/2)/[1-tan�0�5(α/2)]
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sinα·cosβ=(1/2)[sin(α+β)+sin(α-β)]
cosα·sinβ=(1/2)[sin(α+β)-sin(α-β)]
cosα·cosβ=(1/2)[cos(α+β)+cos(α-β)]
sinα·sinβ=-(1/2)[cos(α+β)-cos(α-β)]
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sinα+sinβ=2sin[(α+β)/2]cos[(α-β)/2]
sinα-sinβ=2cos[(α+β)/2]sin[(α-β)/2]
cosα+cosβ=2cos[(α+β)/2]cos[(α-β)/2]
cosα-cosβ=-2sin[(α+β)/2]sin[(α-β)/2]
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tanα+cotα=2/sin2α
tanα-cotα=-2cot2α
1+cos2α=2cos�0�5α
1-cos2α=2sin�0�5α
1+sinα=(sinα/2+cosα/2)�0�5
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sinα+sin(α+2Ï/n)+sin(α+2Ï*2/n)+sin(α+2Ï*3/n)+â¦â¦+sin[α+2Ï*(n-1)/n]=0
cosα+cos(α+2Ï/n)+cos(α+2Ï*2/n)+cos(α+2Ï*3/n)+â¦â¦+cos[α+2Ï*(n-1)/n]=0 以å
sin�0�5(α)+sin�0�5(α-2Ï/3)+sin�0�5(α+2Ï/3)=3/2
tanAtanBtan(A+B)+tanA+tanB-tan(A+B)=0
cosx+cos2x+...+cosnx= [sin(n+1)x+sinnx-sinx]/2sinx
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左边=2sinx(cosx+cos2x+...+cosnx)/2sinx
=[sin2x-0+sin3x-sinx+sin4x-sin2x+...+ sinnx-sin(n-2)x+sin(n+1)x-sin(n-1)x]/2sinx ï¼ç§¯ååå·®ï¼
=[sin(n+1)x+sinnx-sinx]/2sinx=å³è¾¹
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sinx+sin2x+...+sinnx= - [cos(n+1)x+cosnx-cosx-1]/2sinx
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=[cos2x-cos0+cos3x-cosx+...+cosnx-cos(n-2)x+cos(n+1)x-cos(n-1)x]/(-2sinx)
=- [cos(n+1)x+cosnx-cosx-1]/2sinx=å³è¾¹
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