# Carlyle circle

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## English[edit]

### Etymology[edit]

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

### Noun[edit]

**Carlyle circle** (*plural* **Carlyle circles**)

- (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.