sin(α+β)=sinαcosβ+cosαsinβ,
sin(α-β)=sin[α+(-β)]=sinαcos(-β)+cosαsin(-β)=sinαcosβ-cosαsinβ.
cos(α+β)=cosαcosβ-sinαsinβ.
cos(α-β) = cosαcosβ+sinαsinβ
sin(A+B) = sinAcosB+cosAsinB
sin(A-B) = sinAcosB-cosAsinB
cos(A+B) = cosAcosB-sinAsinB
cos(A-B) = cosAcosB+sinAsinB
tan(A+B) = (tanA+tanB)/(1-tanAtanB)
tan(A-B) = (tanA-tanB)/(1+tanAtanB)
cot(A+B) = (cotAcotB-1)/(cotB+cotA)
cot(A-B) = (cotAcotB+1)/(cotB-cotA)
【倍角公式】:
Sin2A=2Sin*CosA
Cos2A=CosA^2-SinA^2=1-2SinA^2=2CosA^2-1
tan2A=(2tanA)/(1-tanA^2)
注:SinA^2 是sinA的平方 sin2(A)
两角和差:
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)
半角公式:
tan(A/2)=(1-cosA)/sinA=sinA/(1+cosA)
cot(A/2)=sinA/(1-cosA)=(1+cosA)/sinA
sin^2(a/2)=(1-cos(a))/2
cos^2(a/2)=(1+cos(a))/2