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!