1. 1 4-5 Isosceles and Equilateral Triangles State and apply the Isosceles Triangle Theorem and its converse State and apply the corollaries for equilateral and equiangular triangles

2. 2 Isosceles Triangle Vocabulary An isosceles triangle has two or more congruent sides. The congruent sides of an isosceles triangle are called the legs. The third side is called the base. The two legs form the vertex angle. The other two angles are called the base angles.

3. 3 Isosceles Triangle Theorem If two sides of a triangle are congruent, then the angles opposite those sides are congruent. C A B

4. 4 Converse of Isosceles Triangle Theorem If two angles of a triangle are congruent, then the sides opposite those angles are congruent. C A B

5. 5 Angle Bisector of Isosceles Triangle The bisector of the vertex angle of an isosceles triangle is the perpendicular bisector of the base.

6. 6 Equilateral and Equiangular Triangles A triangle is equilateral if and only if it is equiangular