So far you've been looking at a very simple version of GeoGebra. Here you can see that a new column has opened up on the left, which shows information about all the elements in your workspace. Try moving points A, B, and C, and watch what happens to the information on the left.[br]
What do you think the values of a, b and c in the column on the left represent? How about the value for poly1?
What kind of a point is point C?
Now use the Regular Polygon tool to add a square to each of the sides of the triangle. Select the tool, then click on Point B, then Point A, then enter 4 in the menu that pops up. Next click on Point A, then Point C, and enter 4. Repeat for side CB. Drag Points A, B, and C around and watch the measurements of poly2, poly3, and poly4.
What do you notice about the sum poly2 and poly3 compared with poly4? If you're not sure, try entering 'poly2+poly3' in the [b]Input Bar [/b]at the bottom of the GeoGebra workspace.