Properties of Special Properties of Special TrianglesTriangles

4-54-5

Objective:Objective:

To use and apply properties of To use and apply properties of isosceles and equilateral isosceles and equilateral

trianglestriangles

Vertex angle

Isosceles Triangle

base

Base angles

legs

If you were to construct an Isosceles Triangle you would:

1. Draw an angle, label it C

2. Mark congruent segments along each side.Label A and B

3. Connect A and B

4. Measure and label base angles.

5. Is there a pattern?

C

AB

Base angles

Isosceles Triangle Theorem

Theorem 4-3 If two sides of a triangle are congruent, then the angles opposite those sides are ________congruent.

Does this theorem apply to an equilateral triangle?

The Isosceles Triangle Theorem applies to equilateral triangles.

ECBA

mm

Find the following:

Example

4.5 p. 254: 1-13 odd,

17, 19B D

E

420

C

A

960

7 cm

7cm

3 cm

6969

3cm

69

69 42

420

3 cm