tan(A+B)=sin(A+B)/cos(A+B)=(sinAcosB+cosAsinB)/(cosAcosB-sinAsinB) 分子分母分别除以cosAcosB(cosA不等于0,cosB不等于0) tan(A+B)=(tanA+tanB)/(1-tanAtanB)若是tan(A-B),则tan(A-B)=(tanA-tanB)/(1+tanAtanB)...