两角和与差公式

sin(a+b)=sinacosb+cosasinb

cos(a+b)=cosacosb-sinasinb

sin(a-b)=sinacosb-cosasinb

cos(a-b)=cosacosb+sinasinb

tan(a+b)=(tana+tanb)/(1-tanatanb)

tan(a-b)=(tana-tanb)/(1+tanatanb)