Download Isosceles and Equilateral Triangles

Warm Up
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Properties of Special
Triangles
Objective:
To use and apply properties
of isosceles and equilateral
triangles
Isosceles Triangle
Vertex
angle
legs
base
Base angles
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
A
Isosceles Triangle Theorem
If two sides of a triangle are
congruent, then the angles opposite
those sides are congruent.
________
B
Base angles
Does this theorem apply to an equilateral triangle?
The Isosceles Triangle Theorem applies to equilateral triangles.
Example
A
69
7cm
E
3 cm
960
420
420
3 cm
C
69
7 cm
B
42
D
Find the following:
mA  69
mB  69
EC  3cm
Isosceles Triangle Theorem
Find x.