function y = asech(z)
%ASECH  Inverse hyperbolic secant.
%   ASECH(X) is the inverse hyperbolic secant of the elements of X.

%   Copyright 1984-2000 The MathWorks, Inc. 
%   $Revision: 5.5 $  $Date: 2000/06/01 00:40:14 $

y = acosh(1./z);
