The Math League
The Math League: Figures and Polygons: Nonagons
This site provides definitions and examples of the various types of polygons including nonagons.
Mr. Martini's Classroom
Mr. Martini's Classroom: Teacher's Figure Library: Geometric Figures
This interactive resource provides an example picture of the geometric figure chosen by students to review.
ClassFlow
Class Flow: Investigating Regular Polygons
[Free Registration/Login Required] In this lesson students are introduced to regular polygons. Students learn how to find the drawing angle of any given polygon, exterior angle, interior angle and the sum of the angles for a regular...
University of Cambridge
University of Cambridge: Nrich: Where Are They?
Test your logic, polygon properties, and pattern recognition skills working on this challenge. Solution included.
SMART Technologies
Smart: Polygons
This SMART Notebook lesson allows students to characteristics of polygons by exploring vocabulary and sample problems.
Math Open Reference
Math Open Reference: Circumcircle
A handy reference guide to circumcircles. It provides definitions and examples that enhance further explanation. Includes links to related topics.
National Council of Teachers of Mathematics
The Math Forum: Plane Figure
This site provides a definition for plane figure (at the top of the page) and a few examples.