function area = triangle_area ( vert1, vert2, vert3 )

%*****************************************************************************80
%
%% triangle_area() returns the area of a triangle.
%
%  Licensing:
%
%    This code is distributed under the GNU GPL license.
%
%  Modified:
%
%    22 April 2023
%
%  Author:
%
%    John Burkardt.
%
%  Input:
%
%    real vert1(2), vert2(2), vert3(2): the vertex coordinates.
%
%  Output:
%
%    real area: the area of the triangle.
%
  area = 0.5 * ...
    ( ...
        ( vert2(1) - vert1(1) ) * ( vert3(2) - vert1(2) ) ...
      - ( vert3(1) - vert1(1) ) * ( vert2(2) - vert1(2) ) ...
    );

  return
end
