# conchoid

[kong-koid]

- a plane curve such that if a straight line is drawn from a certain fixed point, called the pole of the curve, to the curve, the part of the line intersected between the curve and its asymptote is always equal to a fixed distance. Equation: r = b ± a sec(θ).

## Origin of conchoid^{}

Dictionary.com Unabridged
Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

## Examples from the Web for conchoid

### Historical Examples

#### Conchoid′al, pertaining to a conchoid: shell-like, applied to the fracture of a mineral; Concholog′ical, pertaining to conchology.

#### The conchoid has been employed by later mathematicians, notably Sir Isaac Newton, in the construction of various cubic curves.

# conchoid

- geometry a plane curve consisting of two branches situated about a line to which they are asymptotic, so that a line from a fixed point (the pole) intersecting both branches is of constant length between asymptote and either branch. Equation: (x – a)²(x ² + y ²) = b ² x ² where a is the distance between the pole and a vertical asymptote and b is the length of the constant segment

Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012