function value = f1 ( x )

%*****************************************************************************80
%
%% f1() evaluates trigonometric interpolation test function #1.
%
%  Discussion:
%
%    F1(0) does not equal F1(1).
%
%  Licensing:
%
%    This code is distributed under the MIT license.
%
%  Modified:
%
%    28 August 2019
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real x, the evaluation points.
%
%  Output:
%
%    real value, the function value at x.
%
  value = ( x - 0.5 ) .* ( x - 0.25 ) .* ( x - 1.2 ) .* ( x - 2.0 );

  return
end

