This term was first used by Huygens in a letter to Leibniz, where it was described as the evolute of the tractrix and the locus of the mid-point of the vertical line segment between the curves ex and e-x.  
It is the subject of a treatise by David Gregory.  Euler showed that one revolved around its asymptote generates the only minimal surface of revolution.  This term was first used by Huygens in a letter to Leibniz, where it was described as the evolute of the tractrix and the locus of the mid-point of the vertical line segment between the curves ex and e-x.  Its Cartesian equation is given by y equals a times the cosine of x over a, which was found after Jacob Bernoulli issued a challenge to find the equation of the "chain curve."  FTP, identify this curve that is a suspended flexible chain acted on by gravity.
It is the subject of a treatise by David Gregory.  Euler showed that one revolved around its asymptote generates the only minimal surface of revolution.  
catenary