Graph of the mathematical curve known as the Witch of Agnesi. This curve is defined as follows: starting with a fixed circle, a point O on the circle is chosen. For any other point A on the circle, the secant line OA is drawn. The point M is diametrically opposite to O. The line OA intersects the tangent of M at the point N. The line parallel to OM through N, and the line perpendicular to OM through A intersect at P. As the point A is varied, the path of P is the Witch of Agnesi. The curve was studied by Pierre de Fermat in 1630. In 1703, Guido Grandi gave a construction for the curve.