Question

what is the value of tan a * tan b if a+b+c=pai and mangle c is obtuse .
in answer box write answer only i hope gys you will solve my question

Answer 1

$if \: a + b + c = \pi \\ tan(a + b + c) = 0 \\ tan \: a + tan \: b + tan \: c = \\ tan \: a \: tan \: b \: tan \: c \\ as \: c \: is \: obtuse \: so \: tan \: c \: is \: - ve \\ tan \: a + tan \: b + - tan \: c = \\ - tan \: a \: tan \: b \: tan \: c \\ tan \: a \: tan \: b = \frac{tan \: c - tan \: a - tan \: b}{tanc}$