1. Triangle Sum Theorem The sum of the angle measures in a triangle is 180 degrees.

2. Isosceles Triangles a triangle with at least 2 congruent sides

3. Isosceles Triangle The congruent sides are called the legs of a triangle. The angle formed by the legs is the vertex angle. The side of the triangle opposite the vertex angle is the base. The angles that have the base as a side are the base angles.

4. Isosceles Triangle Theorem If two sides of a triangle are congruent, the angles opposite them are congruent.

5. Converse Isosceles Triangle Theorem If two angles of a triangle are congruent, the sides opposite them are congruent.