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>Concepts>Planar Figures, Perimeter (Circumference) and Area in GeoGebra

Planar Figures, Perimeter (Circumference) and Area in GeoGebra

You can use GeoGebra to draw points, lines, and planar figures like polygons, circles, and ellipses. You’ll also learn how you can compute the perimeter/circumference and area of your figures.

GeoGebra Instruction 1

Drawing a Point

1.: Open Algebra View and Graphics View under View in Menu.
2.: Select the Point tool, which is the second tool in Toolbar.
3.: Draw a point in Graphics View by clicking where you want your point.
4.: If you want to hide the axes and the grid lines in Graphics View, click Style Bar in the top-right corner. Click the left-most button to hide the axes. To hide the grid, click the button showing a grid, then select the option which has no grid lines.

GeoGebra Instruction 2

Drawing a Line

1.

Open Algebra View and Graphics View under

View in

Menu.

2.

Select the Line

tool, which is the third tool in Toolbar.

3.

Lines in GeoGebra are made by first drawing two points. GeoGebra then draws the line that goes through them both. Using the steps from Item 4, make the points by clicking where you want them.

4.

If you click the Line

tool again, you’ll open the toolbox for lines. Here you’ll find many alternatives to Line

The second tool in the list is Segment , which lets you draw a line segment between two existing points.
The third tool in the list lets you draw a line segment with a given length.

5.

If you want to hide the axes and the grid lines in Graphics View, click Style Bar

in the top-right corner. Click the left-most button to hide the axes. To hide the grid, click the button showing a grid, then select the option which has no grid lines.

GeoGebra Instruction 3

Drawing a Polygon

1.: Open Algebra View and Graphics View under View in Menu.
2.: Select the Polygon tool, which is the fifth tool in Toolbar.
3.: Draw a polygon by clicking on where you want its vertices to be. When you’ve drawn all the vertices, complete the polygon by clicking on the first vertex you drew.
4.: If you want to hide the axes and the grid lines in Graphics View, click Style Bar in the top-right corner. Click the left-most button to hide the axes. To hide the grid, click the button showing a grid, then select the option which has no grid lines.

GeoGebra Instruction 4

Finding the Perimeter/Circumference of a Figure

1.

Draw your figure in GeoGebra.

If your figure is a polygon, follow Item 2.
If your figure is a circle or an ellipse, you can read their separate entries to learn how to draw them: Entry about circles, Entry about ellipses.

2.

Find the name of your figure in Algebra View. Usually, the first polygon gets the name t1, while circles and ellipses get the name c.

3.

In an empty row in Algebra View, use the command

Perimeter(<Polygon>) if your figure is a polygon. Replace <Polygon> with the name of the figure you got in Step 2.
Circumference(<Conic>) if your figure is a circle or an ellipse. Replace <Conic> with the name of the figure you got in Step 2.

Press Enter. The perimeter/circumference of the figure will be displayed in Algebra View.

GeoGebra Instruction 5

Finding the Area of a Figure

1.

Draw your figure in GeoGebra.

If your figure is a polygon, follow Item 2.
If your figure is a circle or an ellipse, you can read their entries to learn how to draw them: Entry about circles, Entry about ellipses.

2.

Find the name of your figure in Algebra View. Usually, the first polygon gets the name t1, while circles and ellipses get the name c.

3.

In an empty row in Algebra View, use the command

Area(<Polygon>) if your figure is a polygon. Replace <Polygon> with the name of the figure you got in Step 2.
Area(<Conic>) if your figure is a circle or an ellipse. Replace <Conic> with the name of the figure you got in Step 2.

Press Enter. The area of the figure will be displayed in Algebra View.

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