4. Vocabulary
1. Legs of an Isosceles Triangle: The two congruent sides
of an isosceles triangle
2. Vertex Angle:
3. Base Angles:
5. Vocabulary
1. Legs of an Isosceles Triangle: The two congruent sides
of an isosceles triangle
2. Vertex Angle: The included angle between the legs of
an isosceles triangle
3. Base Angles:
6. Vocabulary
1. Legs of an Isosceles Triangle: The two congruent sides
of an isosceles triangle
2. Vertex Angle: The included angle between the legs of
an isosceles triangle
3. Base Angles: The angles formed between each leg and
the base of an isosceles triangle
8. Theorems and Corollaries
Theorem 4.10 - Isosceles Triangle Theorem: If two sides
of a triangle are congruent, then the angles opposite
those sides are congruent
Theorem 4.11 - Converse of Isosceles Triangle Theorem:
Corollary 4.3 - Equilateral Triangles:
Corollary 4.4 - Equilateral Triangles:
9. Theorems and Corollaries
Theorem 4.10 - Isosceles Triangle Theorem: If two sides
of a triangle are congruent, then the angles opposite
those sides are congruent
Theorem 4.11 - Converse of Isosceles Triangle Theorem:
If two angles of a triangle are congruent, then the
sides opposite those angles are congruent.
Corollary 4.3 - Equilateral Triangles:
Corollary 4.4 - Equilateral Triangles:
10. Theorems and Corollaries
Theorem 4.10 - Isosceles Triangle Theorem: If two sides
of a triangle are congruent, then the angles opposite
those sides are congruent
Theorem 4.11 - Converse of Isosceles Triangle Theorem:
If two angles of a triangle are congruent, then the
sides opposite those angles are congruent.
Corollary 4.3 - Equilateral Triangles: A triangle is
equilateral IFF it is equiangular
Corollary 4.4 - Equilateral Triangles:
11. Theorems and Corollaries
Theorem 4.10 - Isosceles Triangle Theorem: If two sides
of a triangle are congruent, then the angles opposite
those sides are congruent
Theorem 4.11 - Converse of Isosceles Triangle Theorem:
If two angles of a triangle are congruent, then the
sides opposite those angles are congruent.
Corollary 4.3 - Equilateral Triangles: A triangle is
equilateral IFF it is equiangular
Corollary 4.4 - Equilateral Triangles: Each angle of an
equilateral triangle measures 60°
12. Example 1
a. Name two unmarked congruent angles.
b. Name two unmarked congruent
segments
13. Example 1
a. Name two unmarked congruent angles.
b. Name two unmarked congruent
segments
14. Example 1
a. Name two unmarked congruent angles.
b. Name two unmarked congruent
segments
21. Example 2
Find each measure.
180 - 60 = 120 120 ÷ 2 = 60
= 60°
a.
b. PR
Since all three angles will be 60°, this is an
equilateral triangle, so PR = 5 cm.
