Cuemath
Cuemath: Regular Polygon
Introduces the concept of regular polygons along with regular polygon examples, not regular polygons, irregular polygons, and area of a regular polygon. Check-out the solved examples for better understanding and try your hand at solving...
University of Cambridge
University of Cambridge: Nrich: Diagonal Trace
Develop problem solving skills working with pentagons and then check your results.
University of Georgia
University of Georgia: Inter Math: Heptagon
This site gives the general definition of a heptagon with several diagramed examples. There are links to related terms, everyday examples, challenging problems, more information, and the interactive check point involving heptagons...