Tutorial:Basic Algebraic Input, Commands and Functions

Tips and Tricks

• Name a new object by typing name = into the input bar in front of its algebraic representation.
  Example: P = (3, 2) creates point P.

• Multiplication needs to be entered using an asterisk or space between the factors.
  Example: a*x or a x

• GeoGebra is case sensitive! Thus, upper and lower case letters must not be mixed up.
  • Points are always named with upper case letters
    Example: A = (1, 2)

• • Vectors are named with lower case letters
    Example: v = (1, 3)

• • Segments, lines, circles, functions… are always named with lower case letters.
    Example: circle c: (x – 2)^2 + (y – 1)^2 = 16

• • The variable x within a function and the variables x and y in the equation of a conic section always need to be lower case.
    Example: f(x) = 3*x + 2

• If you want to use an object within an algebraic expression or command you need to create the object prior to using its name in the input bar.
  • y = m x + b creates a line whose parameters are already existing values m and b (e.g. numbers / sliders).
  • Line[A, B] creates a line through existing points A and B.
• Confirm an expression you entered into the input bar by pressing the Enter key.
• Open the help window for using the input bar and commands by selecting Help from the Help Menu (or shortcut F1).
• Error messages: Always read the messages – they could possibly help to fix the problem!
• Commands can be typed in or selected from the list next to the Input Bar.
  Hint: If you don’t know which parameters are required within the brackets of a certain command, type in the full command name and press key F1 to open the GeoGebra Wiki.

• Automatic completion of commands: After typing in the first two letters of a command into the Input Bar, GeoGebra tries to complete the command.
  • If GeoGebra suggests the desired command, hit the Enter key in order to place the cursor within the brackets.
  • If the suggested command is not the one you wanted to enter, just keep typing until the suggestion matches.

Constructing Tangents to a Circle (Part 1)

Open the dynamic worksheet [to a Circle]. Follow the directions on the worksheet in order to find out how to construct tangents to a circle.

Discussion

• Which tools did you use in order to recreate the construction?
• Were there any new tools involved in the suggested construction steps? If yes, how did you find out how to operate the new tool?
• Did you notice anything about the toolbar displayed in the right applet?
• Do you think your students could work with such a dynamic worksheet and find out about construction steps on their own?

Constructing Tangents to a Circle (Part 2)

What if my Mouse and Touchpad wouldn’t work?

Imagine your mouse and / or touchpad stop working while you are preparing GeoGebra files for tomorrow’s lesson. How can you finish the construction file?

GeoGebra offers algebraic input and commands in addition to the geometry tools. Every tool has a matching command and therefore could be applied without even using the mouse.

Note: GeoGebra offers more commands than geometry tools. Therefore, not every command has a corresponding geometry tool!

Preparations

• Open a new GeoGebra window.
• Show the Algebra View and Input Bar, as well as Coordinate Axes (View Menu)