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########################################################################
##
## Copyright (C) 1994-2025 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING. If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################
## -*- texinfo -*-
## @deftypefn {} {@var{y} =} asec (@var{x})
## Compute the inverse secant in radians for each element of @var{x}.
## @seealso{sec, asecd}
## @end deftypefn
function y = asec (x)
if (nargin < 1)
print_usage ();
endif
y = acos (1 ./ x);
endfunction
%!test
%! rt2 = sqrt (2);
%! rt3 = sqrt (3);
%! v = [0, pi/6, pi/4, pi/3, 2*pi/3, 3*pi/4, 5*pi/6, pi];
%! x = [1, 2*rt3/3, rt2, 2, -2, -rt2, -2*rt3/3, -1];
%! assert (asec (x), v, sqrt (eps));
%!error <Invalid call> asec ()
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