Google Classroom
GeoGebraGeoGebra Classroom

Diagonals in Polygons

Use the segment tool (first click on the line icon Toolbar Image, then the segment icon Toolbar Image) to draw the maximum number of triangles you can, inside the polygons. Only use the polygon’s vertices as points, such that no 2 diagonals overlap.
In your notebook record the number of triangles made inside each polygon. Create a chart like this one to help you.
Image

How does this second table relate to the first one? What connections can be made?

What is the sum of interior angles of a polygon with 9 sides? Explain your thinking.

Come up with a formula in the form of , where S is the sum of interior angles and n is the number of sides. Using your work with the diagonals and the table, explain why it works.