Pentagon Interior and Exterior Angles: Quick Exploration
In the Geometry app below,
1) Use the POLYGON 
tool to construct pentagon ABCDE.
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 pentagon, making
sure to add the Greek letters (and not single numerical values)! If you forget how to do this,
click here to see it again in the context of a triangle.
tool to construct pentagon ABCDE.
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 pentagon, making
sure to add the Greek letters (and not single numerical values)! If you forget how to do this,
click here to see it again in the context of a triangle. 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 pentagon?
Here, in this app, we have a pentagon with its EXTERIOR ANGLES shown. Calculate the SUM of the measures of these exterior angles here in this app.
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 pentagon? Be specific in your response.