Special Triangle Conjectures

SWBAT prove and understand conjectures of isosceles and regular triangles using in

class notes and activities

The Symmetry Line in Isosceles Triangles

• Construct a large isosceles • You can just create two lines using the

measurements on your ruler, then just connect the endpoints of the two lines.

The Symmetry Line in Isosceles Triangles

• Now, measure your vertex angle on your isosceles triangle

• Divide that measurement in half, and create a new line which would be the angle bisector

• Now label your points like this:

• What do we notice about the segments BD and DC?

• What about the angles ADB and ADC

• Finally, what do we notice about triangles ABD and ACD?

B

A

CD

The Symmetry Line in Isosceles Triangles

The Symmetry Line in Isosceles Triangles

• So, the symmetry line in isosceles triangles is also the angle bisector

Now, Let’s Prove the Vertex Angle Bisector

Conjecture

Let’s Practice!

Let’s Practice!

Let’s Practice!