
with h(t) = √(f^{2}(t)+g^{2}(t)) Given a curve C_{1}(f(t), g(t)) and a fixed point O(0,0). Draw lines l through O that intersect C_{1} in Q. Then the conchoid is defined as the collection of points P (on l) for which PQ is equal to a constant a. This conchoid is a generalization of the 1st curve that was named as a conchoid, the (simple) conchoid that is derived from the straight line.
In the following table some conchoids have been collected:
The conchoid of Dürer does not belong to this family, it is another variation on the conchoid. 