# Triangle Interior and Exterior Angles: Quick Exploration

- Author:
- Tim Brzezinski

## In the Geometry app below,

1) Use the POLYGON tool to construct triangle

*ABC*. 2) Select the ANGLE tool. Then click anywhere inside the polygon. 3) Go to the Algebra view (click calculator icon upper left). 4) Calculate the sum of the measures of the interior angles of this triangle.*Be sure to add the Greek letters when doing so!*(See the video right below this app to see how to quickly do this in GeoGebra).## Quick (Silent) Demo

Select the MOVE tool in the app above. Move any one (or more) of the triangle's vertices around. What can we conclude about the **sum of the measures of the interior angles** of any triangle?

## Here, in this app, we have a triangle with its EXTERIOR ANGLES shown. Calculate the SUM of the measures of these exterior angles here in this app.

## Question 2

Select the MOVE tool. Move any one (or more) of the triangle's vertices around.
What can we conclude about the **exterior angles** of this triangle? *Be specific in your response. *