When Desmos fails

I have become a great fan of Desmos, a free web-based graphing calculator app. It is easy to use and remarkably powerful, providing evaluations, graphs, tables, and probably a lot of other things that I haven’t learned yet. What’s especially important is the pairing of “web-based” and “free,” as that combination means that all students can use it.

The use of color in graphs is particularly effective, especially for applications like linear programming:

Desmos regions 1












Two other features that I like are the use of sliders to animate graphs and the side-by-side displays of graphs and equations (or inequalities in this case), which you can see in this zoomed-out shot:

Desmos regions 2








Desmos also seems to work every time. Personally I’ve never known it to fail. And yet…

Here we have a post titled “When Desmos Fails,” by Patrick Honner, a self-described “huge Desmos fan.” Honner illustrates a situation where the technology produces an incorrect graph when one zooms way in and around a hole in a graph. He makes an important observation:

Lots of interesting questions emerge from such anomalies, and these are great questions for students to explore.  In doing so, they’ll not only learn some mathematics and some computer science, but they’ll also develop a healthier relationship with technology, by learning to understand how it does what it does, and perhaps more importantly, what it doesn’t do.

Read the entire post at the link, and especially the comments. Often comments aren’t worth reading, but here they’re essential to understanding what’s going on.


Categories: Math, Teaching & Learning, Technology