function fx1 = p13_fx1 ( x )

%*****************************************************************************80
%
%% P13_FX1 evaluates the derivative of the function for problem 13.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    07 May 2011
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, real X, the abscissa.
%
%    Output, real FX1, the first derivative of the function at X.
%
  slope = 0.00000000001;
  fx1 = slope;

  return
end
