如题所述
tan(a+b)
=sin(a+b)/cos(a+b)
=(sinacosb+cosasinb)/(cosacosb-sinasinb)......分子分母同时除以cosacosb
=(tana+tanb)/(1-tanatanb)
=sin(a+b)/cos(a+b)
=(sinacosb+cosasinb)/(cosacosb-sinasinb)......分子分母同时除以cosacosb
=(tana+tanb)/(1-tanatanb)
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