function value = kepler_fp ( x )

%*****************************************************************************80
%
%% kepler_fp evaluates the derivative of a kepler function.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    20 September 2019
%
%  Input:
%
%    real x, the current estimate for the value of E.
%
%  Output:
%
%    real value, the derivative of the kepler function.
%
  value = - 1.0 + 2.0 * cos ( x );

  return
end

