I have a 15 year old with several undesirable traits. We had an intense discussion two days ago about whether “clothes picked up from the floor in your room” is satisfied by “dirty clothes simply kicked under the bed.” I prevailed, but an hour or so later he gave me a note saying “Here is your Christmas message, Dad.”

Here is his note. This is the Christmas midterm for our readers. What does the note say?

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Fascinating, as Mr. Spock famously and fictionally said. I will send this my mathgeek son for interpretation.

Henry,

re your most recent comment on my persmickety questions, I’m glad to hear from you and I appreciate your thoughtfull comment. I will respond as thoughtfully as I can, but not now. I just had a pleasant dinner with my wife and her son, and I have had a little too much wine to be thorough in my response. It’s 19.32 hours in Stockholm.

Best wishes,

Ron

u * r * ( Surface area of a cylinder with no top ) * jerk —

You aren’t getting anything for Christmas, Jerk.

Joel

There would appear to be a “dx” missing. Put otherwise, there is a dangling integration. It sounds painful.

I see what you mean. I can’t remember enough calculus to know whether or not the twerp got it wrong, but I hope he did. Or is the dx tacitly implied? I will rub it in if he got it wrong.

At the beginning of this semester he was nervous about having signed up for calculus: it seemed like a forbidding mountain to him. He asked me one day “what is a derivative?” I gave him the easy half hour of it, no epsilon delta stuff, explaining that if x was the position of a car, the first time derivative of x was speed, the second acceleration, and so on. I told him that he wouldn’t encounter higher derivatives this term but I did point out that the third derivative, the change in acceleration, was called the “jerk term.” I noticed then a transient gleam in his beady eyes as he filed that away in the mischief locker in his brain.

Henry

It is good to see someone making creative use of the quotient rule. He may have left the dx off because typically the quotient rule is written (udv – vdu)/v^2 with no dx’s. I’m not sure what the significance of the surface area of a cylinder is. Likely he is doing problems involving minimizing the surface area of a cylindrical pot of a fixed volume, or minimizing the cost perhaps, where the sides and base have different costs per square cm.

Sorry, I made an error, should have written vdu – udv. Your son has it correct. I usually think of it as (u’v – v’u)/v^2.

Don’t hassle him about the missing dx. He has probably only just barely begun to study anti-derivatives if he is in Calc I

. He is a smart kid!

I suspect the message was: U R A Jerk.

It is topically rude, but in the context of teenage rage quite normal. Quite a creative message.

We had an intense discussion two days ago …As the parent of a similarly inclined teenager, I’ve been conditioned to avoid the intense discussion. The Hegelian dialectic is a tool used by teenagers to abuse their parents. Now I use the dictator plan: I lay out duties. If not followed, there are consequences, usually the loss of a privilege.

U R A Jerk

I agree. If would seem reasonable for “A” to represent the surface area of a cylinder.

Intense discussions with intense offspring are a specialty in our household. After many years, I’ve learned to ride the beasts till the the barrel wearing clowns come running out.

I like a rollicking discussion about the feasibility of solar power, or the implications of worm-hole technology. On the matters of TV time or number of candy bars, not so much.

Maybe the surface area of a cylinder refers to a can or a bag. Then it would be: U R a Can of Jerk.