# Trisectrix

Mathematica Notebook for This Page.

## History

## Description

Trisectrix is a general name for curves that can be used to trisect a angle. The name trisectrix is often reserved for a special case of limacon of Pascal, which we discuss here. Other famous trisectrix include trisectrix of Maclaurin and conchoid of Nicomedes.

Trisectrix can be generated as a conchoid or epitrochoid. (See: limacon of Pascal for definition).

## Formula

- Polar: r == (1+2 * Cos[t]) , 0 ≤ t < 2 π.
- Cartesian: (-2 x + x^2 + y^2)^2 == x^2 + y^2

## Properties

### Trisecting a Angle

Let P be any point on the outer loop of the curve. The angle formed by P, {1,0}, {3,0} is three times larger than the angle {0,0}, P, {1,0}.

### Graphic Gallery

Parallels of trisectrix.

## Related Web Sites

See: Websites on Plane Curves, Printed References On Plane Curves.

The MacTutor History of Mathematics archive