4-6 Isosceles and Equilateral
Triangles
Ms. 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/Practice
1. 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
50
12.
AAS or ASA
Mixed Review
20
90
40