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Table of Contents for the Geometry course "One Mathematical Cat, Please!"

GeoGebra Basics

Jump right to the exercises!

This tutorial firms up many of the concepts introduced in GeoGebra Worksheet: Triangles,
and also introduces some new features of GeoGebra.

In the View submenu, a checked item means that it is visible.
These work as a toggle; when you click on a checked item, it becomes unchecked.
When you click on an unchecked item, it becomes checked.


Axes visible; no Grid	Grid visible; no Axes	Axes visible; Grid visible	no Axes; no Grid

FREE OBJECTS are ones that can be freely moved with the MOVE tool.
DEPENDENT OBJECTS depend on something else.

Here, points A and B are free; MIDPOINT was constructed as the midpoint of A and B :
free and dependent objects

If you right-click on a dependent object, you can see its dependency:

If you right-click on an object and check Trace on , then you can see a "trace" of its movement in the geometry window.
Below, both A and MIDPOINT are being traced.
(Point A was moved with the MOVE tool; MIDPOINT followed accordingly.)
To make a trace disappear, uncheck Trace on .

Uncheck Show object to make an object disappear; its label also disappears.
Such an object is called a HIDDEN OBJECT.
Notice that the bullet next to a hidden object is HOLLOW; the bullet next to a visible object is FILLED-IN.

If desired, you can uncheck Show label to make only a label disappear:
make a label disappear

GeoGebra has a wonderful "undo" feature.
If you ever goof anything up, just select Edit-Undo from the MENU.
You can undo multiple items.
You can redo anything that you undo.
undo and redo

To get a submenu from the toolbar, you must click the small arrow in the bottom right corner of a tool.
If you click anywhere else, you'll just make the tool active instead of getting the submenu.
getting a submenu

To rename an object, right-click on the object and select Rename .
GeoGebra won't allow two different objects to have the same name:
it automatically renames, if needed, to prevent this from happening.

The easiest way to start a fresh drawing pad is to select File-New .
You are given the option of saving the current file.

GeoGebra uses lowercase Greek letters to label angles.
For now, you should know the first three lowercase Greek letters: alpha, beta, and gamma.

Sometimes, labels get positioned in an ugly way.
You can use the MOVE tool to adjust the position of the labels.


ugly labeling	better labeling

You can display text in the Geometry Window using the INSERT TEXT tool, which is under the SLIDER tool.
INSERT TEXT tool:

After you select a tool, instructions on its proper use appear to the right of the toolbar:
insert text instructions

Always look in this space to see how to use a tool!
For the INSERT TEXT tool, click anywhere in the drawing pad, and a text box appears:

STATIC TEXT is text that just sits there–it is static–it doesn't change.
Just type static text in the text box and click APPLY.
Use the MOVE tool to put the text where you want it.

DYNAMIC TEXT is text that changes.
It's much more exciting and useful!
QUOTATION MARKS (",") are VERY IMPORTANT when you're creating dynamic text.
Characters inside quotation marks are displayed exactly as they appear.
Outside the quotation marks, a "+" sign is used to put things together.
When you type a GeoGebra object outside the quotation marks, its current value will be displayed.

Here are some examples:


Type this in the text box...	After pressing APPLY, here's what you see. As you move A around, the coordinates will change.


Type this in the text box...	After pressing APPLY, here's what you see.


Type this in the text box...	After pressing APPLY and moving point A , here's what you see.

You can change the properties of displayed text by right-clicking on the text box with the MOVE tool active,
and selecting Properties... .

text properties

Changing the font, size, and color are all routine.
You see the changes immediately in the Geometry Window (even without pressing APPLY).

Two of the tabs, however, deserve some discussion: Position and Advanced .

You can set up text to follow (say) a point around the screen.
Just type the name of the point in the Position box:


Set up your text to follow point A...	... and as you move A, the text follows!

GeoGebra uses x(A) and y(A) to denote the x-value and y-value of a point A .
Suppose you only want to show some text when the x-value is greater than zero:
you can use the Advanced tab to do this!


Set up the desired condition.	Here, the x-value is 1.2, which is greater than zero. Thus, the text is showing.	Here, the x-value is -0.18, which is less than zero. Thus, the text is not showing.

Indeed, every GeoGebra object has its own Properties... box.
This Properties... box gives you some special labeling features:
you can show only the NAME of an object; both the NAME and VALUE; or only the VALUE.


set up point A to show both name and value...	... and here's what you'll see