tan(A+B)=(tanA+tanB)/(1-tanAtanB)

问题描述:

tan(A+B)=(tanA+tanB)/(1-tanAtanB)

sin(a+b)=sinacosb+sinbcosa
cos(a+b)=cosacosb-sinasinb tan(a+b)=sin(a+b)/cos(a+b),然后分子分母同时除以cosacosb 那么就有tan(A+B)=(tanA+tanB)/(1-tanAtanB)

tan(A+B)=sin(A+B)/cos(A+B)=(sinAcosB+sinBcosA)/(cosAcosB-sinAsinB)分子,分母同时除以cosAcosB得:=(sinA/cosA+sinB/cosB)/(1-sinAsinB/cosAcosB)=(tanA+tanB)/(1-tanAtanB)