Durer's conchoid

Durer's conchoid

[′du̇r·ərz ′käŋ‚kȯid]
(mathematics)
A plane curve consisting of points that lie on a variable line passing through points Q and R and are a constant distance a from Q, where Q and R have cartesian coordinates (q,0) and (0, r) and q and r satisfy the equation q + r = b, where b is a constant.