From proposition I.6 Prove that in a triangle in which two angles are equal, the sides opposite the to these angles must be congruent Assume that you are working in Hilbert plane. Proposition I6: if the base angles are equal the triangle is isosceles.

Assuming two triangles are congruent if 2 corresponding sides and the angle between the two sides are congruent (SAS), then prove the following statement: If in one triangle two angles are congruent, then the sides opposite the equal angles also congruent.

Statement and reason number one.