http://www-history.mcs.st-and.ac.uk/Curves/Circle.html

Circle. Cartesian equation: x2 + y2 = a2 or parametrically: x = a cos(t), y = a sin(t) Polar equation: r = a. Click below to see one of the Associated curves.

http://jwilson.coe.uga.edu/EMT668/EMAT6680.F99/Kim/emat6690/instructional%20unit/circle/Circle/Circle.htm

Circle. History. The study of the circle goes back beyond the recorded history. The invention of the wheel is a fundamental discovery of properties of a circle.

https://en.wikipedia.org/wiki/Circle

The circle has been known since before the beginning of recorded history. Natural circles would have been observed, such as the Moon, ...

https://circlesonly.wordpress.com/category/history-of-circles/

Posts about History of Circles written by circlesonly.

https://www.smithsonianmag.com/travel/world-full-circles-180954529/

Mar 12, 2015 ... A fascination and interest in circles predates recorded history, with many ancient cultures finding approximations for pi—the ratio of a circle's ...

https://nrich.maths.org/2561

This article for pupils gives some examples of how circles have featured in people's ... so let's explore some of the most famous and mysterious circles in history.

https://www.newworldencyclopedia.org/entry/Circle