1/[tan(A/2)]=tan(π/4+B/2)由此证A+B=π/2在△ABC中,已知[tan(A/2)+tan(A/2)*tan(B/2)]/(1-tan(B/2)=1,则有1/[tan(A/2)]=tan(π/4+B/2),由此证A+B=π/2

问题描述:

1/[tan(A/2)]=tan(π/4+B/2)由此证A+B=π/2
在△ABC中,已知[tan(A/2)+tan(A/2)*tan(B/2)]/(1-tan(B/2)=1,
则有1/[tan(A/2)]=tan(π/4+B/2),由此证A+B=π/2

tan(π/4+B/2)=(tanπ/4+tanB/2)/(1-tanπ/4tanB/2) 公式 tan(a+b)=(tana+tanb)/(1-tanatanb)=(1+tanB/2)/(1-tanB/2)= 1/tanA/2 已知∴(1+tanB/2)tanA/2=1-tanB/2 去分母tanA/2+tanA/2tanB/2=1-tanB/2 去括号∴tanA/...