Hello there.
I've always wondered why didn't HP design a calc to compete directly with the SR50. For example, the SR50 had at its inception hyperbolic and inverse hyperbolic functions as well as a summation key for its lone memory register.
So, why wasn't it until the HP32E that hyperbolic functions appeared? Also, why wasn't memory arithmetic (even just addition) added until after the 35?
Edited: 24 Mar 2012, 3:52 p.m.
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the SR50 had at its inception hyperbolic and inverse hyperbolic functions [...] So, why wasn't it until the HP32E that hyperbolic functions appeared?
Presumably because HP's marketing people determined that very few customers needed hyperbolic functions. Back then ROM was expensive enough that adding hyperbolic functions would actually add to the cost, or require that you left something else out to make room. When designing a product, you have to make tradeoffs.
Things are much different now. The cost per bit of ROM had dropped by more than six orders of magnitude, so now the decision as to what features to put into a highend calculator aren't driven by the cost of the ROM. (For lowend calculators, there are still constraints on ROM size for different reasons.)
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Also, why wasn't memory arithmetic (even just addition) added until after the 35?
The 35 was the world's first handheld scientific calculator. It's amazing that they were able to make the thing at all, thus it is not surprising that the feature set is fairly minimal. HP wasn't even sure that the thing would sell, but they obviously expected that if it did, they would introduce even better models later.
There was a very good RPN with hyperbolic trig available during the runs of the 45, 55, and 21. It just wasn't an hp.
Corvus 500
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Presumably because HP's marketing people determined that very few customers needed hyperbolic functions.
Very true. I can't remember EVER using hyperbolic functions for any real work.
The SR50 was TI's first real scientific calculator, arriving more than two years after the HP35.
The 1974 SR50 was an amazing machine in its era, in many ways superior to the 1972 HP35 and in a few ways even better than the 1973 HP45. I was an EE student at Ga. Tech all during this time, during which the SR50 ($170, $785 in 2012), HP35 ($300, $1385 in 2012), and HP45 ($400, $1847 in 2012) were all way out of my financial reach. I finally bought an SR50 after getting a few paychecks after graduation. (I still have it, and it still works as well as when new.) Most of us then considered the SR50 to be TI's competition to the HP35, and not near the equal overall of the HP45. Hyperbolic functions are good for feature bragging rights, but are seldom required. It would have been inconceivable to me at the time that HP needed to do anything in response to the SR50 other than lower their prices. The SR51 and 51A were TI's competition to the HP45.
IMHO, the SR50 is TI's most attractive calculator ever. From the time of the subsequent SR50A and 51A, TI has seemed determined to produce the ugliest handhelds from that point on. HP tried to compete in the ugly arena from 1986 through 2006, but I think the award still goes to TI.
I used an SR50 (a generous gift from my parents) in college and it was an excellent calculator. Quite wellbuilt and much more attractive than what came later from TI. I don't recall ever using the hyperbolic functions, though.
The Corvus 500, you say. Hmm...That and the APF Mark 55 were the ones that 'Everything You've Always Wanted To Know About RPN...' was written for.
Thanks for correcting my history. Now this all makes sense. I'm not certain why but, I thought the SR50 came out early in the calculator era. Boy, was I off by a bit of time!
Edited: 24 Mar 2012, 5:38 p.m.
Accurately computing cable lengths in power transmission lines does require hyperbolic functions. They are easily definable in terms of exponentiation and logarithms though.
I must admit, I've not really used hyperbolic functions for anything beyond play, however they do appear in all manner of obscure places.
The logistic distribution from statistics can be defined in terms of COSH & TANH.
Complex trig functions involve the hyperbolics of course.
The Jacobi elliptic functions include both trig and hyperbolic functions  a kind of extension that unifies both.
The Gudermannian function links trig functions and hyperbolic functions without involving complex numbers.
 Pauli
Certainly there are engineering uses for hyperbolic trigonometric functions. However, they are in general far less common than circular trig. Historically engineers were accustomed to using the exponential function multiple times to compute hyperbolic functions, and square root and natural log to compute their inverses, whether using tables, slide rule, or electronic calculator. On an RPN calculator, that tends to be easier than on an "algebraic" calculator, which may be why HP didn't consider providing hyperbolic functions to be a high priority.
For instance, on an RPN calculator, to compute a hyperbolic sine, you can use the keystroke sequence:
 ENTER^
 e^x
 x<>y
 CHS
 e^x
 
 2
 /
And for inverse hyperbolic sine:
 ENTER^
 x^2 (or ENTER^ *)
 1
 +
 sqrt(x)
 +
 ln
Similar key sequences are easily derived for the other hyperbolic and inverse hyperbolic functions.
I remember there was a parabolic approximation formula for cable length. That's what they might have used before scientific calculators were widely available.
An alternative keystroke sequence for sinh(x) is
e^x
ENTER
1/x

2
/
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For instance, on an RPN calculator, to compute a hyperbolic sine, you can use the keystroke sequence:
Way too complicated. ;) Gerson already posted the usual (shorter) sequence. Replace the Minus by a Plus and get cosh(x) instead.
Hyperbolic functions are good examples for tasks that look easy, or may even appear trivial, while there actually are some numeric pitfalls that can substantially degrade the resulting accuracy. Here e^x1 and ln1+x come to the rescue. This approach is also used in the respective program on this site.
Dieter
Probably off topic, but can you tell me about the power connector on the TI? I just "inherited" one. I've found how to replace the NiCad cells and the power requirements on Datamath, but I haven't found what the connector is.
As a GT ME, I had a few classes in that awful round EE building across from Textiles. I don't remember its name... nor do I remember ever doing any real engineering involving the hyperbolics.
Bill
The plug to the old style SR TIs is a 2.5mm mono jack. The adapter output is AC if I'm not mistaken. The calculator needs a working battery to be fed by the adapter.
Thanks, Marcus. I thought I had tried that and it didn't fit, but apparently not.
Bill