tan(a+2b)=(tana+tan2b)/(1-tanatan2b)
tan2b=2tanb/(1-tan^2b)
tana=1/7,tanb=1/3带入
tan2b=2tanb/(1-tan^2b)=3/4
tan(a+2b)=(tana+tan2b)/(1-tanatan2b)=1
tan(a+2b)=(tana+tan2b)/(1-tanatan2b)
tan2b=2tanb/(1-tan^2b)
tana=1/7,tanb=1/3带入
tan2b=2tanb/(1-tan^2b)=3/4
tan(a+2b)=(tana+tan2b)/(1-tanatan2b)=1