Isoceles Triangle Theorems

Define: Isosceles Triangle


Name the base angles.

Name the vertex angle

Name the legs

Name the base

Drag the vertices of the triangle and observe the angle measurements. What do you notice? Write a conjecture about the base angles of an isosceles triangle.

Isosceles Triangle Theorems Part 2

Drag a vertex of the triangle until two of the angles are congruent. What do you notice about the sides of the triangle? Write a conjecture about the congruent angles and the sides opposite them.

Angle Bisector in An Isosceles Triangle
 Triangle CAB is an isosceles triangle.  The base is segment CB and the legs are segments CA and BA.  Segment AD bisects , the vertex angle of the triangle.

Drag a vertex of the traingle. What do you notice about segments CD and DB?

What can you conclude that segment AD does to segment CB?

What type of angles are and ?

Write a conjecture that summarizes your findings about the angle bisector, segment AD, of the vertex angle in an isosceles triangle and its base, segment CB.