You should first determine the colour and the brush style of the fill style. You can do so by accessing the tool bar on the right side of your screen.

After the third point has been determined, the entire section will be drawn.

With the aid of this section you can perform several little investigations. For instance, you could drag and move one of the points I, J or K if you click the “drag button”.


Or you could launch one of these points by clicking the   button. And you could even launch several points at a time by pressing the  button. 

After pressing one of these buttons you can sit back and watch the section change but you could also right-click on the filled area which will bring up a menu that allows you to perform even more actions:

You can move the object in such a way that the plane is portrayed at full size which creates the possibility of treating the object as if it were part of plane geometry! After you have finished your investigation you can always return to the three-dimensional model.
 

Another wonderful option is to split the object along the filled section. An animation will show the process and after its completion you will have the possibility of removing one of the two parts and continue your investigation with just one single part.

And if you are into rotations you can right-click on a line segment and rotate the object around the axis you just chose. The picture alongside shows the menu as it would appear should you click on line segment CJ in the drawing above.