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

%   Copyright (c) 1984-98 by The MathWorks, Inc.
%   $Revision: 5.3 $  $Date: 1997/11/21 23:28:06 $

y = acosh(1./z);
