function area = disk_area ( r )

%*****************************************************************************80
%
%% disk_area() returns the area of a disk of radius R.
%
%  Licensing:
%
%    This code is distributed under the MIT license. 
%
%  Modified:
%
%    04 November 2022
%
%  Author:
%
%    John Burkardt
%
%  Input:
%
%    real r: the radius of the disk.
%
%  Output:
%
%    real area: the area of the disk.
%
  area = pi * r * r;

  return
end
