There's this one proof that's been bugging me and I can't seem to get it at all.(adsbygoogle = window.adsbygoogle || []).push({});

Given: Isosceles triangle ABC (A being the vertex) and line AF as the < bisector of <BAC's exterior angle.

Prove: Line AF is parallel to base BC

I have no clue where to start on this...I tried making two congruent triangles but don't have enough information to prove they are congruent so I don't know what to do now. I'd really appreciate some help. Thanks.

**Physics Forums | Science Articles, Homework Help, Discussion**

Join Physics Forums Today!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

# Homework Help: Need help on proving something

**Physics Forums | Science Articles, Homework Help, Discussion**