of a curve
The planar curve obtained by increasing or decreasing the position vector of each point of a given planar curve by a segment of constant length $l$. If the equation of the given curve is $\rho=f(\phi)$ in polar coordinates, then the equation of its conchoid has the form: $\rho=f(\phi)\pm l$. Examples: the conchoid of a straight line is called the Nicomedes conchoid; the conchoid of a circle is called the Pascal limaçon.
|[a1]||J.D. Lawrence, "A catalog of special plane curves" , Dover, reprint (1972) Zbl 0257.50002|
Conchoid. Encyclopedia of Mathematics. URL: http://www.encyclopediaofmath.org/index.php?title=Conchoid&oldid=36903