高考英語在線輔導(dǎo)

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
tan(a/2)=(1-cos(a))/sin(a)=sin(a)/(1 cos(a))三角和
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)