A math riddle is:

*Q: Why did the mathematician work from home?
A: Because he could only function in his domain.*

The joke has been cited in print since at least 2012.

Peter Friedman

@MrFriedmanMath

Why did the mathematician only work from home?? Check back later for the answer. #mathjokes

4:02 PM · Oct 16, 2012·Twitter for iPad

psssssst malone

@redeyetreeefrog

Why did the mathematician work from home? Because he could only function in his domain

9:57 PM · Nov 7, 2012·Twitter Web Client

cicadian rhythms

@Guderjahn1

Why did the mathematician work from home? She couldn’t function outside her domain

#Mr.Moodyjokes

@Llamajuice1 @NEDC7

8:05 PM · Dec 3, 2012·Twitter for iPhone

Drake Akens

@DrakeQRandom

Why did the mathematician work from home? Because he can only function in his domain.

9:56 PM · Jan 16, 2014·Twitter Web Client

Daily Kos

*New Day Cafe: Cool Crossed Puns...Part Two*

The Marti for New Day Cafe

Tuesday April 09, 2019 · 9:30 AM EDT

(...)

28. WHY DID THE MATHEMATICIAN WORK FROM HOME?

Because he could only function in his domain.

Quora

*What are some ridiculous puns?*

Amit Kumar, Attended ISB. GMAT 750.

Answered Sep 6, 2020

Here are some good (meaning terrible) puns that I have collected over the years.

(...)

27. Why did the mathematician work from home?

Because he could only function in his domain.

Lorraine Jo King

@lahlahbean

#sillysaturday

Why did the mathematician work from home? Because he could only function in his domain.

2:29 AM · Feb 22, 2020·Crowdfire App