Triangle Congruence Cases

2nd Case of Congruence - Angle-Side-Angle

1- Why is the proof strategy correct?

Check all that apply

Proof steps.

2- Move the "Steps" selector and follow the proof steps. Do you understand? If you didn't understand, write what you didn't understand.

Analysis

Change the position of point C so that you have an obtuse triangle. Do any of the steps in the proof have changed? Which ones?

Exterior angles

In order to understand the proof of the 4th postulate, we need to explore a property of the exterior angle of the triangle. First, we will see what is an exterior angle of a convex polygon.

Analysis

Check the box show / hide angle measurements. Change the position of points A, B or C. Compare an exterior angle with its non-adjacent ones. What can you see?

Observation

You may have noticed that the exterior angle is equal to the sum of the non-adjacent interior angles. The argument for this property will be discussed in the chapter that deals with parallelism.

Finish the Proof

Prove that AB cannot be greater than A'B'.