tan(A+B/2)×tan(C/2)=

问题描述:

tan(A+B/2)×tan(C/2)=

tan[(A+B)/2]
=tan[(180° -C)/2]
=tan[90° -C/2]
=cot(C/2)
原式
=cot(C/2)*tan(C/2)
=1