function centroid = cone_centroid_3d ( r, xc, yc, zc, xh, yh, zh )

%% CONE_CENTROID_2D returns the centroid of a cone in 3D.
%
%  Modified:
%
%    04 May 2005
%
%  Author:
%
%    John Burkardt
%
%  Reference:
%
%    Adrian Bowyer and John Woodwark,
%    A Programmer's Geometry,
%    Butterworths, 1983.
%
%  Parameters:
%
%    Input, real R, the radius of the circle at the base of the cone.
%
%    Input, real XC, YC, ZC, the coordinates of the center of the circle.
%
%    Input, real XH, YH, ZH, the coordinates of the tip of the cone.
%
%    Output, real CENTROID(3), the coordinates of the centroid of the cone.
%
  centroid(1:3) = 0.75 * [ xc, yc, zc ] + 0.25 * [ xh, yh, zh ];