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// Scilab ( http://www.scilab.org/ ) - This file is part of Scilab
// Copyright (C) INRIA
// Copyright (C) 2012 - Scilab Enterprises - Adeline CARNIS
// This file must be used under the terms of the CeCILL.
// This source file is licensed as described in the file COPYING, which
// you should have received as part of this distribution. The terms
// are also available at
// http://www.cecill.info/licences/Licence_CeCILL_V2.1-en.txt
function x=cosm(a)
// cosm - computes the matrix cosine
//%CALLING SEQUENCE
// x=cosm(a)
//%PARAMETERS
// a : square hermitian or diagonalizable matrix
// x : square hermitian matrix
rhs = argn(2);
if rhs <> 1 then
error(msprintf(gettext("%s: Wrong number of input argument(s): %d expected.\n"),"cosm",1));
end
if type(a)<>1 then
error(msprintf(gettext("%s: Wrong type for input argument #%d: Real or complex matrix expected.\n"),"cosm",1));
end
[m,n]=size(a);
if m<>n then
error(msprintf(gettext("%s: Wrong size for input argument #%d: Square matrix expected.\n"),"cosm",1));
end
if a==[] then x=[],return,end
if norm(imag(a),1)==0 then
x=real(expm(%i*a))
else
x=0.5*(expm(%i*a)+expm(-%i*a));
end
endfunction
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