Question 395924

in triangle {{{abc}}}, an exterior angle at {{{A}}} measures {{{40}}}

 which is the longest side of the triangle?


An {{{exterior}}} angle and an {{{interior}}} angle must be equal {{{180}}}.

Therefore we would do {{{180 - 40}}}, which would give us 

{{{140=interior_angle}}}  at {{{A}}} . 


We also know that {{{140}}} is an {{{obtuse}}} angle because it is greater than 

{{{90}}} degrees, and a triangle can only have {{{one}}} obtuse angle.

Since the {{{longest}}}{{{ side }}}{{{always}}}{{{ lies}}}{{{ opposite}}} the {{{largest}}}{{{ angle}}}, the longest side must be {{{bc}}}.