Download 4-5 Congruent Triangles - Isosceles and Equilateral (orig

Congruency and Triangles
Featuring Isosceles and Equilateral Triangles
Lesson Objectives
 Learn the properties of isosceles and equilateral
triangles.
 Learn the properties of perpendicular bisectors
Isosceles Triangles

The congruent sides of an isosceles triangle are its legs.
The third side is the base. The two congruent legs form
the vertex angle. The other two angles are the base angles.
Isosceles Triangles: Theorem 4-3

If two sides of a triangle are congruent then the
angles opposite those sides are congruent.
Isosceles Triangles: Theorem 4-3

Proof for theorem 4-3.
Theorem 4-4
Converse of the Isosceles Triangle Theorem
 If two angles of a triangle are congruent then
the sides opposite those angles are congruent.
Corollaries to Theorems 4-3 and 4-4
Your turn!
 Answer the following questions.