Edit->Add->geometry
menu to make a new 2-d geometry
session. This will open in a level a subsession at the left,
the 2-d screen in the middle, and the controls at the right. If there
are parameters, they will be below the controls at the right.
The subsession is a list of commandline levels. Evaluation of
a commandline level will automatically reevaluate all levels
below (i.e. with a higher level number), therefore if you use
one level to define an object and modify the definition of this
object later, all objects depending on this object will be modified.
Modification of a level defining a point or a 1-d parameter can be
done interactively with the mouse either in the geometric screen or in the
parameter area (below the controls).
Inside the geometric screen, the mouse can be used to define new points or segments, or to move an existing point. To define a new point, just click somewhere not near another point or segment. To define a segment, push the mouse button at the beginning, move the mouse, release the mouse at the end of the segment (if you release the mouse out of the screen, the segment will be cancelled). To move an existing point, click on it to select it, then push the mouse and move the mouse, release it at the new postion. You can currently not draw a more complex object with the mouse, you must use the commands of the Geo menu in a separate commandline level.
To erase a geometrical object, just select the levels in the
subsession at the left, and use the Edit->Suppress levels
menu.
For example, you can click three points with the mouse,
this will create 3 levels with definitions for points A,B,C.
Then you can make the circle containing A, B, C with the
circonscrit
command (menu Geo->Circles
) by
entering the following command in the next commandline
c:=circonscrit(A,B,C)