Picture Perfect Parabolas (Desmos Activity)

I’m intrigued by the Desmos Activity Builder and where it might be useful for my students.  One of the first activities I’ve made is based on the idea of fitting graphs to photos of naturally-occurring or man-made parabolas, which I first encountered in Adrian Oldknow’s book Teaching Mathematics Using ICT back in 2004.

In my activity, students are asked to fit some parabolas to photos of bridges and fountains.  And a banana.  They are also asked to explain their thought processes before they attempt the graphical transformations.

If you haven’t encountered the Desmos Teacher Site yet, it’s great fun, and really well thought-out.  You can watch what all your students are doing/have done from your computer and target your help and questioning where they are most needed.

I love watching students get excited by graphs (’cause graphs are just wonderful, let’s be honest here) and I love using resources in my classroom, both from the front and amongst the students, that make graphs (“I don’t like drawing graphs”…”I don’t get graphs”) and the principles of graphing more accessible and easier to understand.  I’ve been giving some thought to why Desmos seems to achieve this so well and I think it’s because without having to physically draw the graphs all the time students can spend more time thinking about the principles behind them.  From the front of the classroom I can display a quadratic and show the roots/intersections with axes/vertex immediately and talk about these features.  I don’t waste time drawing the graph (by now I’m quite happy my students can plot a curve), and if I want to change my example I only have to alter a number or move a slider.

Of course, graphing software has existed for a long time, so what I’m talking about is nothing new, but before now I’ve never used graphing software that is so quick and easy to create with and, more importantly, that is this high-quality for free!

I’m starting to sound like an advert now, so I’ll stop, but if you are a maths teacher and haven’t tried it yet, do so soon.



  1. I’ve had the same experience with students attitudes toward graphing. The Desmos interface is intuitive, and seems to remove barriers for many students. Precise drawing of graphs on paper is difficult – especially for students who are still struggling conceptually. Instead of getting stuck on the mechanics, they are able to really play with the ideas. And it is highly motivating to match graphs to pictures as you’ve done with your activity. I’ve found that when we go back to paper and pencil, they have made great strides.

    Thanks for articulating this so well, and for sharing your excellent parabola activity.


    • No problem, Nat, thanks for commenting. I agree – the intuitive interface of Desmos is one of its biggest pros.

      When I’m teaching something like this topic I like to approach it in many different ways to help students grasp it, which was the motivation for the activity.


Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Google photo

You are commenting using your Google account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s