Isosceles, Equilateral, and Right Triangles

1
Section 4-6

• Isosceles, Equilateral, and Right Triangles

2
Using Properties of Isosceles Triangles
3
Base angles

• The two angles adjacent to the base

Vertex angle

• The angle opposite the base

4
Isosceles Triangle
Vertex Angle
Base Angles
Base
5
Base angles theorem

• If two sides of a triangle are congruent, then
  the angles opposite them are congruent.

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A
B
C
, then
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Converse of the base angles theorem

• If two angles of a triangle are congruent, then
  the sides opposite them are congruent.

8
A
B
C
, then
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Corollaries

• If a triangle is equilateral, then it is
  equiangular.
• If a triangle is equiangular, then it is
  equilateral.