Fix a plane algebraic curve in real 2-space, a point P in 2-space, and a positive real number d. Associated to this data is a conchoid.

This is the set of points Q in R2 such that

  1. the line through P and Q intersects the curve
  2. the intersection point is distance d from Q.

For examples see conchoid of Nicomedes, conchoid of de Sluze.

Con"choid (?), n. [Gr. ; shell + form: cf. F. conchoide.] Geom.

A curve, of the fourth degree, first made use of by the Greek geometer, Nicomedes, who invented it for the purpose of trisecting an angle and duplicating the cube.


© Webster 1913.

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