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## -*- texinfo -*-
## @deftypefn {} {} asech (@var{x})
## Compute the inverse hyperbolic secant of each element of @var{x}.
## @seealso{sech}
## @end deftypefn

function y = asech (x)

  if (nargin < 1)
    print_usage ();
  endif

  y = acosh (1 ./ x);

endfunction


%!testif ; ! ismac ()
%! v = [0, pi*i];
%! x = [1, -1];
%! assert (asech (x), v, sqrt (eps));

%!test <*52627>
%! ## Same test code as above, but intended only for test statistics on Mac.
%! ## Mac trig/hyperbolic functions have huge tolerances.
%! if (! ismac ()), return; endif
%! v = [0, pi*i];
%! x = [1, -1];
%! assert (asech (x), v, sqrt (eps));

%!error <Invalid call> asech ()