From GeoGebra Manual
Redefining objects is a very versatile tool to change a construction. Please note that this may also change the order of the construction steps in the Construction Protocol.
Note: The redefined element can only depend on elements defined before -- you may need to change order of the elements in Construction Protocol.
In GeoGebra, an object may be redefined in different ways:
- Select Move Tool and double click on any object in the Algebra View.
- For free objects an editing field is opened allowing you to directly change the algebraic representation of the object. Hit the Enter-key in order to apply these changes.
- For dependent objects the Redefine dialog is opened allowing you to redefine the object.
- Select Move Tool and double click on any object in the Graphics View. This opens the Redefine dialog and allows you to redefine the object.
- Change any object by entering its name and the new definition into the Input Bar.
- Open the Properties Dialog and change the definition of an object on tab Basic.
- From GeoGebra 4.2, the Redefine dialog of an object, which was just created, is immediately opened by typing any letter on the keyboard.
Note: Fixed objects cannot be redefined. In order to redefine a fixed object, you need to free it first using tab Basic of the Properties Dialog.
Example: In order to place a free point A on an existing line h, you first need to double click on the point A to open the Redefine dialog window. Then, enter the command
Point[h]in the appearing text field and press the Enter-key. To remove point A from this line and make it free again, you need to redefine it to some free coordinates like (1, 2).
Example: Another example is the conversion of a line h through two points A and B into a segment. Open the Redefine dialog for line h and enter the command
Segment[A, B]in the appearing text field.