University of Georgia
University of Georgia: Inter Math: Nonagon
This site gives the general definition of a nonagon with examples of a regular (convex) and irregular concave nonagons. There are links to related terms, challenging problems, more information, and the interactive check point involving...
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.