4-6 Isosceles and Equilateral TrianglesMs. Andrejko

Real World

Vocabulary

•Legs- the two congruent sides of an isosceles triangle

•Vertex Angles- the angle with sides that are the legs

•Base Angles- the two angles formed by the base and the congruent sides

Theorems/Corollaries

•T 4.10- If 2 sides of a triangle are congruent, then the angles opposite those sides are congruent

•T 4.11- if 2 angles of a triangle are congruent then the sides opposite those angles are congruent

•C 4.3- A triangle is equilateral if and only if it is equiangular

•C 4.4- Each angle of an equilateral triangle measures 60°.

Examples

Practice

Examples

Refer to the figure•1. If AC ≅ AD, name two congruent

angles.

•2. If BE ≅ BC, name two congruent angles.

Practice

Refer to the figure•3. If ∠EBA ≅ ∠EAB, name two congruent

segments.

•4. If ∠CED ≅ ∠CDE, name two congruent segments.

Example/Practice1. m∠KML

2. m∠HMG

3. m∠GHM

4. If m∠HJM = 145, find m∠MHJ.

5. If m∠G = 67, find m∠GHM.

Example

Practice

Mixed Review

110

70

30

Mixed Review

12.

50

AAS or ASA

Mixed Review

20

90

40