# Quadrilateral: Exterior Angle Sum Activity

Before you begin:
Feel free to move this quadrilateral's vertices (corners) wherever you'd like.

**You can control the size of the red exterior angle by using the red slider. You can control the size of the blue exterior angle by using the blue slider.**This applet works best if this quadrilateral is kept**convex**. If you don't remember what this means, click here for a refresher. Interact with the applet for a minute or two. Then answer the question that follows.What can you conclude about the measures of the exterior angles of ANY QUADRILATERAL? How do you know this?