Carlyle circle

The idea of using such a circle to solve a quadratic equation is attributed to Thomas Carlyle (1795–1881).

Carlyle circle (plural Carlyle circles)

1. (mathematics) A certain circle in a coordinate plane associated with a quadratic equation, having the property that the solutions of the equation are the horizontal coordinates of the intersections of the circle with the horizontal axis.

   Carlyle circles have been used to develop ruler-and-compass constructions of regular polygons.