Armchair detective an arm-chair, my brother would be the greatest criminal agent that ever lived." "The first example of armchair detecting can be found in the work of Edgar Allan Poe. In "The Mystery of Marie Rogêt" (1842), C. Auguste Dupin, working wholly from newspaper accounts, arrives at the correct explanation for a young woman's mysterious disappearance." Baroness Orczy's Old Man in the Corner sits in a restaurant and talks to an acquaintance about cases, almost always finishing by revealing that he has solved the crime. A more literal use of this term can be found in Rex Stout's Nero Wolfe novels
Dupin cyclide also used to refer to a more general class of quartic surfaces which are important in the theory of separation of variables for the Laplace equation in three dimensions. Dupin cyclides were investigated not only by Dupin, but also by A. Cayley und J.C. Maxwell. Today, Dupin cylides are used in computer-aided design (CAD), because cyclide patches have rational representations and are suitable for blending canal surfaces (cylinder, cones, tori, and others). There are several equivalent definitions of Dupin cyclides. In formula_1, they can be defined as the images under any inversion of tori, cylinders and double cones. This shows