Hello, My name is Ryan and I use desmos frequently in my classroom. I was wondering if there is any way to place imaginary numbers or complex numbers into desmos like you can with the TI calculators when you change the mode from real to a + bi? If so this would be very helpful for those students who do not have calculators of their own to work at home on our remote days or for homework.
2 Likes
Hi Ryan, as best as I can tell, Desmos does not currently support complex numbers but has received some requests to add support for them (e.g. this tweet). You’re definitely welcome to re-request this feature so it gets more attention!
You can make Desmos activities that handle specific uses for complex numbers - it would be quick to make an activity that adds complex numbers, for example - or to avoid reinventing the wheel you can direct your students to other online resources like Symbolab or WolframAlpha.
The idea of using Desmos to create a complex number calculator tickled my fancy, so here’s a prototype:
I’m sharing this mostly as a curiosity - if I were sharing a resource for my students, I’d share one (like one linked above) that’s better than this 
3 Likes
In Desmos, you can represent complex numbers using the standard mathematical notation, where i represent the imaginary unit such as to represent the complex number 3+2i you would write it as 3+2i
Cool cool cool!
When I type 3+2i, Desmos wants to add a slider for i.
What am I missing?
1 Like
Hey Steve! I’m assuming your response is to Mateo’s post, and you entered 3+2i in an otherwise empty expression list. My understanding is still what I posted before, that Desmos does not have built-in support for complex numbers. I’m not sure what Mateo is referring to.
Thanks. You have totally harshed my mellow.
I’ve been trying to read your code, and it’s pretty wild. It looks like a sixth-order frequency approximation. I’m thinking about doing it directly.
1 Like
Wild is a good word for it haha. I hadn’t cracked that open for quite a while - it looks like I was handling f(i) that were polynomials in i, and I was extracting up to 12 coefficients of f(i) via derivatives. Then I added and subtracted all the coefficients to simplify it down to a + bi. I remember thinking there must be a better way, and I’m eager to see whatever you come up with!
I’m afraid you may be disappointed. While I’d like a complex package, I got away with much less for a specific purpose. I wrote a visualization of a geometric proof of the fundamental theorem of algebra that a dth degree polynomial over the complex plane has d roots.
(there is clearly a bug …)
1 Like
is it possible to plot expressions with imaginary (i) in desmos?
For eg: e^ix
It seems Desmos got updated, and now supports complex numbers using standard complex notation. You need to go into the settings and check “Complex Mode”, then it should work as Mateo said previously.
2 Likes
I wanted to check in on this. I see that the desmos grapher now allows use of complex numbers. Is there a way to use input to plot a complex number with this new feature?
I can type “2+3i” in a graph and it will plot the point. However, when I have a student input and plot the input, I cannot get the point to graph. Running some debugging, I see that when I type a number like “3i” in a student input, the graph only sees “3” and not the imaginary number i.
I’d love to do this without the use of patterns, if possible.
I couldn’t figure out how to get the graph component to accept student answers with i when in complex mode.
I did, however, realize that I could just use xyLine(…,“i”, “y”) using the y-intercept as the real number and the slope as the imaginary part. Much simpler than using patterns. Here is a link to the activity: