Question

prove that tan(A+B) + tan C=0

Answer 1

A+B+C= 180'
A+B =180'-C
tan(A+B+C) = tan(180) =0
$( tan(a + b) + tan(c)) \div (1 - \tan(a + b) \tan(c) )$
=0
=> tan(a+b) + tan(c) =0