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# conchoid

[kong-koid]
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noun Geometry.
1. 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 .css-1fxfie5{font-size:22px;}@media (max-width:768px){.css-1fxfie5{font-size:18px;margin:0 10px 10px 0;word-break:break-all;word-wrap:break-word;-webkit-hyphens:auto;-moz-hyphens:auto;-ms-hyphens:auto;hyphens:auto;line-height:22px;}}conchoid

From the Greek word konchoeidḗs, dating back to 1790–1800. See conch, -oid
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.

Chambers's Twentieth Century Dictionary (part 1 of 4: A-D)

Various

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

British Dictionary definitions for conchoid

# conchoid

noun
1. 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