# Celebratio Mathematica

## Joel Hass

### Some observations concerning Joel Hass, or how we decided to write How to Ace Calculus

#### I

I spent a leave year at UC Dav­is in or­der to work with Joel and Abby Thompson. I was as­signed the job of teach­ing busi­ness cal­cu­lus. The first day of class, I went in and sat in the front row, pre­tend­ing to be a stu­dent. Then Joel came in and pre­ten­ded to be me. He began with a so­li­lo­quy.

“My name is Pro­fess­or Colin Adams and I’m very ex­cited to be here this year. I’m vis­it­ing from a little col­lege back east that none of you will have heard of. I want to wel­come all of you to cal­cu­lus, and for most of you who are first year stu­dents, to UC Dav­is. I just want you to know I am here for you all. My fo­cus is on you. Any time, just drop by to see me. My job as a fac­ulty mem­ber is to be avail­able for you 24 hours a day, 7 days a week.

Now we are go­ing to start with a quick re­view of in­equal­it­ies.”

Joel wrote $$(x-2)/x < 7$$ on the board.

“To solve this, the first thing we do,” he said, “is mul­tiply through by the de­nom­in­at­or.” He wrote $x-2 < 7x.$

At this point I raised my hand.

“Ex­cuse me, Pro­fess­or,” I said, “but isn’t true that if the $$x$$ is neg­at­ive, you have to change the dir­ec­tion on the in­equal­ity?”

Joel turned to look at me with an icy stare.

“If you’re so damned smart, why don’t you teach the class?”

And with that he threw down the chalk and stormed out of the room.

Or at least, that’s the way it was sup­posed to go. Un­for­tu­nately, as he was say­ing his part, an­oth­er stu­dent yelled out, re­fer­ring to chan­ging the dir­ec­tion on the in­equal­ity, “No, it’s not!” And then there was bed­lam as stu­dents ar­gued wheth­er or not the dir­ec­tion on the in­equal­ity should be changed. So when Joel said his piece and stormed out, most of the stu­dents couldn’t hear what he said.

But at any rate, I stood up, picked up the chalk and said, “All right I will.” Stu­dents said, “What are you do­ing? Where did the pro­fess­or go?” I said, “he said if I’m so smart I should teach the class, so I will.” And with that, I fin­ished the in­equal­ity and con­tin­ued to go over back­ground ma­ter­i­al.

Then I said, “He left these syl­labi. I guess I will hand them out.” By the end of the class peri­od, about half the stu­dents un­der­stood what had happened. But the oth­er half were still ask­ing, “Why are we listen­ing to this guy?” By the next class, after stu­dents had a chance to talk, they all un­der­stood it was a joke and the rest of the quarter went very well.

#### II

Joel, Abby and I went to eat one day at the Chinese res­taur­ant in town. At lunch, we got to talk­ing and we de­cided that someone should write a hu­mor­ous sup­ple­ment to cal­cu­lus that put everything in col­lo­qui­al terms and that ex­plained everything in easy to un­der­stand lan­guage. By the end of the lunch we were very ex­cited about the pro­ject.

That pro­ject be­come the two books How to Ace Cal­cu­lus and How to Ace the Rest of Cal­cu­lus which have now to­geth­er sold over 100,000 cop­ies. Joel’s claim was that on av­er­age, for jokes that are out there, one in ten can be turned in­to a math joke. I was skep­tic­al at first, but it turned out Joel was right. Here is an ex­ample that is a Joel ori­gin­al.

Two cal­cu­lus stu­dents are walk­ing in a field and they come across a big deep hole, so deep they can­not see the bot­tom in the dark­ness be­low.

“I won­der how deep it is,” says the first.

“Here. Help me roll this rail­road tie over the edge,” said the second. “Then we can count how long it takes to hit the bot­tom and use cal­cu­lus to de­term­ine the depth.”

So they roll the rail­road tie over to the edge and push it over. As they are count­ing the seconds, they are sur­prised when a goat sud­denly runs up to the edge and dives over.

“That was weird,” said the first, as they peered after it.

Then from off in the dis­tance they hear a voice.

“Ex­cuse me,” yells a farm­er from the edge of the field, “but have you seen my goat?”

The stu­dents look at each oth­er, and then the second yells back, “Yes, a goat just jumped in this hole.”

“Oh, that can’t be my goat,” yells back the farm­er. “My goat is roped to a rail­road tie.”

Colin Adams is Thomas T. Read Pro­fess­or of Math­em­at­ics at Wil­li­ams Col­lege, Wil­lam­stown, Mas­sachu­setts. He writes “Math­em­at­ic­ally Bent”, a column for the Math­em­at­ic­al In­tel­li­gen­cer, and is the au­thor of The Knot Book, ac­claimed for its lu­cid­ity on ad­vanced top­ics in knot the­ory. He is coau­thor with Joel Hass and Abi­gail Thompson of How to Ace Cal­cu­lus and How to Ace the Rest of Cal­cu­lus. He has been a fel­low of the Amer­ic­an Math­em­at­ic­al So­ci­ety since 2012.