
 A summary of the definitions and properties of the Jacobian elliptic functions 
  The 12 Jacobian elliptic functions are denoted by two letters taken from the quartet s, c, d, n and may be classified into four groups, each with three members, according to the second letter of the function's name. 
  The most popular Jacobian elliptic functions is a copolar trio of sine amplitude elliptic function  sn(x,k), cosine amplitude elliptic function  cn(x,k), and delta amplitude elliptic function  dn(x,k). 
  The functions sn(x,k), cn(x,k), and dn(x,k) are real valued when their argument is real, and modulus k is either real or purely imaginary. 
 www.cmmp.ucl.ac.uk /~jlg/Elliptic/appendix.html (352 words) 
