If you do not know what perimeter is, perimeter is the sum of the lengths of all the sides.

To find the perimeter using Geogebra, click on the angle icon and look for distance or length and click on it. After that click on the sides to find the length of each side. Then, just add the numbers the find the perimeter.

To find the perimeter mathematically, use the distance formula for each side. You should find that all the sides are 5. Add them together to get the perimeter, which is 20.