Geometric proof- isosceles triangle

WITHOUT USING A PERPENDICULAR BISECTOR to the base(making two triangles)and allowing for ONLY ONE extra auxiliary/constructed line Prove: If the base angles of a triangle are congruent, then the triangle is isosceles, in 8-12 two column steps
A.  Draw and label a diagram that includes:
1.  A triangle with each vertex and the given information labeled
2.  All other information needed to present the proof

B.  Construct a formal proof of the theorem including:
1.  Given statement
2.  Other statements that lead to a proof of the theorem
3.  A reason for each step
4.  A conclusion that proves the theorem

-Cannot be used- The theorems- If the bases angles are congruent, then the triangle is isosceles.

The altitude of an isosceles triangle is a perpendicular bisector.

Do not assume it is isosceles to prove it is isosceles or assume it can be cut into two congruent triangles by using a perpendicular bisector without proving it first.