1-12 Chapter 1: Learning the Basics
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Constructing Objects
(Continued)
4.
Move the cursor as follows so that the message
Perpendicular bisector of this side of the triangle
appears.
When the cursor is in unoccupied space in the drawing
window, the
#
appears. Move the cursor near a side of
the triangle. The cursor changes from the
#
to the
$
with
the message
Perpendicular bisector of this side of the triangle
.
(If the cursor is near a vertex of the triangle, the cursor
message
This point
appears.)
Click once, and the perpendicular bisector of the side of
the triangle appears.
Handling ambiguities
When two or more objects simultaneously occur at the location of the pointer, the
magnifying glass
*
cursor and the cursor message
Which object?
appear. Press and hold down the mouse to see the
options in a dialog box. Select an object by pointing to the appropriate choice in the box and
releasing the mouse.
When multiple objects are present, they are listed in the order in which they were created.
Selecting an object causes it to display in marquee outline. You can move (drag) it to a new
location if it is an independent object and the
Pointer
tool is selected. Click in unoccupied space to
deselect the object. If you are using a construction tool, the object is selected for the construction.
Determining dependent and independent objects
All objects are created using one or more points. The manner in which you create an object
determines whether it is dependent or independent of the object. This distinction becomes very
important with respect to dragging
objects. An example of this distinction is given after the section
“Dragging.”
A point constructed by itself is called a
basic point
.
An
independent object
is an object created using only basic points. Independent objects can be
moved (dragged) but not modified directly. By moving the basic points used for their construction,
you can modify them indirectly.
A
dependent object
is an object constructed using an independent object (or another dependent
object). Dependent objects cannot be moved (dragged) or modified directly. You can move or
modify them indirectly by moving the basic points or independent objects responsible for their
existence.
The more elaborate a construction becomes, the more difficult it can be sometimes to distinguish
these types. However, the Cabri Geometry II software will assist you.
Perpendicular bisector of this side of the triangle
