Math2
Math2: Circles
This site has many useful formulas and examples relating to circles, including related definitions, circumference of a circle, area of a circle, length of a circular arc, area of a circular sector, equation of a circle in cartesian...
Curated OER
Educational Technology Clearinghouse: Clip Art Etc: Fibula
A brooch, consisting of a pin, and of a curved portion furnished with a hook. The curved portion was sometimes a circular ring or disc, the pin passing across its centre and sometimes an arc, the pin being as the chord, of the arc. The...