Curious Sticker on the Back of an HP-35


Ignoring the fact that this is mis-advertised as a programmable calculator, take a look a the trig function sticker on the back of this HP-35..

Was this sticker offered by HP or possibly one of the companies that made aftermarket products?


I doubt it came from HP. Also interesting, the S/N says Version 3, but the front label says Version 2.


Since it's far from being coherent, I bet that label was made by somebody else, maybe even DIY.



I'd agree with Walter - probably by somebody who didn't trust his/her memory of trig functions!


Or it's someone who can't remember the name of the famous Indian Chief, SOH CAH TOA


Ya know, if you can't spell ... like I can't spell ... I could never figure out if it was "saw coe toa" or "sow ca toa". I was taught "South Of Halifax Comes A Hundred Tons Of Apples" way back in high school (in Halifax, Nova Scotia of course). It just seemed a bit easier to me since you couldn't confuse the A and O order. (Dimwit that I am...)


I like that one!


This xkcd strip seems appropriate here:

xkcd: Los Alamos

Nigel (UK)


As a non-native english speaker I had to look up the SOH-... and found this one on Wikipedia:

Another method is to expand the letters into a sentence, such as "Some Old Hippy Caught Another Hippy Trippin' On Acid".

You Americans are funny ;-))




I think this last one is ENTIRELY APPROPRIATE for a calculator of this vintage.

However, I don't think the hippies were carrying the HP-35s at Woodstock. (I know my dates are off but it made me laugh to think a tripping hippie would need to remember trigonometry)


I didn't know what this was all about until I looked up the Wikapedia reference. I don't think that I have known anyone who used any of these memory aids for trigonometric relationships. So, I am curious. Did the participants in this forum use this sort of stuff?

In seventh grade geography I was introduced to the memory aid HOMES as a way to remember the names of the Great Lakes. But the teacher commented that it was far better to work from a visualization of the lakes.



Opposite over hypotenuse. Adjacent over hypotenuse. Opposite over adjacent.


I'm with Forrest.

I had never heard of SOCATOA (or whatever) until I started teaching Phsyics I in 2000 (some 32 years after I learned trig).


Same on this side of the pond. No memory aids (Eselsbrücken) in use for such stuff.



I remember being told to remember SOHCAHTOA by my high school trig teacher as a help in talking the NY State Regents Exam. But I found that learning how to spell such a word took the same effort as just learning the definitions of the functions.


I never heard of it before this forum. Not at school, not at university doing mathematics nor doing postgraduate mathematics.

- Pauli


Yah, yah, yah. I hear that everyone here "just gets" the trigonometric relationships -- and considering some of the spelling capability, it might be just as well :-) For the rest of us slightly dyslexic fools (some with several university degrees, including "physics"!), we sometimes could use a crutch or two. But do we all need it? Naw, but it sure is more fun to know!

I am wondering what you used to remember the resistor colour codes? Mine was a bit racy and probably not entirely appropriate in this day and age (suitably modified for a public audience):

"Bad boys [relish] our young girls but Violet goes willingly."

Oh, but surely y'all just got those as well! :-D

Or how about: "Many velvet elephants met jolly Santa under North Pole." Ooops! I guess that doesn't work anymore...

"30 days has September, April, June, and November, all the rest have 31 save February." Or the knuckles trick.

For me, I am lucky if I remember where my car keys are (or even, "where did I park that darn car?")...



I hear that everyone here "just gets" the trigonometric relationships

At the bottom line, you have to remember just one, e.g. sin = opposite / hypotenuse. Then you know cosine being "the other leg". And everything else follows. Feasible, isn't it? Even many engineers know it ;-)



Have to admit I use (a slightly racier version of) Neil's resistor code!

Depends, perhaps, on your field: I never needed a mnemonic for the planets, but I'm an astronomer (although not a planetary one).

On the other hand, if you want to know "what star is that" when looking up at the sky, DON'T ask a professional. You are much better off with a good amateur for that! We tend to look at much (!) fainter stuff, and just type coordinates in to the computer which controls whatever telescope we are using.


Back in the 1940s and 1950s most trigonometry tests were closed book. Students were expected to know the basic trigonometric relationships. No one would have objected to the use of one of the mnemonic tricks as a memory aid. But if a student had written the mnemonic in the palm of his hand or somewhere on his slide rule it would have been considered cheating. So, wasn't the sticker on the back of an HP-35 a case of cheating?

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