Closed Investigation: Finding the Area of a Triangle using the Geogebra Ipad App

Since I work in a 1:1 Ipad School, I decided to finally try out the Ipad Geogebra App. The main content objectives are obvious from the title. Possibly of more importance, the Mathematical Habit objective was to understand that we could utilize technology to help quickly confirm, but not necessarily prove, our conjectures.

I went through a few of the basic functions of the app on the Apple TV, gave out the worksheet below and let them get going. Whilst I understand that there is always a “tinkering stage” to any new piece of technology, I thought that the use of the app was simple enough so that they wouldn’t have to spend too much time familiarizing themselves with it (Ha, I’m in my seventh year of teaching – I should know better with Year 7/Grade 6!)

So it turns out that many did have trouble familiarising themselves with the software (Note to self: showing often doesn’t imply learning) and more annoyingly, it turned out that with the red triangle embedded in the rectangle, the area function couldn’t pick out the triangle area from the rectangle area.


Luckily, I quickly saw that it gives the area of both the rectangle and triangle in the side toolbar (poly1 and poly2) so the investigation wasn’t so badly interrupted.

Next step is to get them using the app to show why we can calculate the area of a parallelogram in the same way we do with a rectangle and then move onto sliders and rotations to find the formula for the area of a trapezium (Next Big Objective: The area of many shapes can be developed from the area of a rectangle).


@Geogebra Team – Great work creating this app! I wonder if there’s any chance of doing some thing about the following stuff:

1. The issue mentioned above – when you want the area of a shape inside a shape,  the only way to do it is to look at the algebra view, anyway of distinguishing between shapes?

2. The angle slider maybe shouldn’t use alpha because there’s no way of putting alpha into the rotation function – maybe set the letter a as default?

3. Is there any way of copying and pasting things on the app?

4. It’s currently quite difficult to edit a script by touching the part of the script you want to change. I wonder if a python style cursor can be developed to do this?


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