function variance = disk_variance ( a, b, c )

%*****************************************************************************80
%
%% DISK_VARIANCE returns the variance of points in a disk.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    17 March 2016
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, real A, B, C, the parameters of the disk.
%    The disk is centered at (A,B) and has radius C.
%    0.0 < C.
%
%    Output, real VARIANCE, the variance.
%
  variance = 0.5 * c * c;

  return
end
