Quadratrix of Hippias
The quadratrix was discovered by Hippias of Elias in 430 BC, 
and later studied by Dinostratus in 350BC (MacTutor Archive). It can be used for Angle Trisection or, more generally, division of anAngle into any integral number of equal parts, and Circle Squaring. In Polar Coordinates,
so
which is proportional to the Cochleoid.
References
Lawrence, J. D. A Catalog of Special Plane Curves. New York: Dover, pp. 195 and 198, 1972. Lee, X. ``Quadratrix of Hippias.''http://www.best.com/~xah/SpecialPlaneCurves_dir/QuadratrixOfHippias_dir/quadratrixOfHippias.html MacTutor History of Mathematics Archive. ``Quadratrix of Hippias.''http://www-groups.dcs.st-and.ac.uk/~history/Curves/Quadratrix.html.
- Diagonal (Polyhedron)
- Diagonal Ramsey Number
- Diagonal Slash
- Diagonal (Solidus)
- Diagonals Problem
- Diagram
- Diameter
- Diameter (General)
- Diameter (Graph)
- Diamond
- Dice
- Dichroic Polynomial
- Dido's Problem
- Diesis
- Diffeomorphism
- Difference
- Difference Equation
- Trigonometry Values Pi/4
- Trigonometry Values Pi/5
- Trigonometry Values Pi/6
- Trigonometry Values Pi/7
- Trigonometry Values Pi/8
- Trigonometry Values Pi/9
- Trigyrate Rhombicosidodecahedron
- Trihedron