POWERS OF NUMBERS

[aurelio]

Excuse me for my trivial question, but how happened that the function (calculated by an internal routine) y^x changed starting from the HP45 after to has been, on the HP35, x^y ?

[trojdor]

I don't know about the 'official' reason, but at the time...when I was actively using both...I remember thinking the newer/45 way felt more logical within the RPN 'postfix' philosophy.
(You first enter a number, then you apply an operation to it. You don't enter the operation first, ala algebraic.)

It also seems easier (to me) when using the 1/x in conjunction with the y^x in order to do various roots of numbers, particularly if they're already on the stack as the result of a previous operation.
For instance, if I've already got a 729 on the x register, and I want to do a cube root, it's as simple as 3, 1/x, y^x, and I've got 9.

mike

[aurelio]

(04-30-2021 08:20 PM)trojdor Wrote:  I don't know about the 'official' reason, but at the time...when I was actively using both...I remember thinking the newer/45 way felt more logical within the RPN 'postfix' philosophy.
(You first enter a number, then you apply an operation to it. You don't enter the operation first, ala algebraic.)

mike

Thank-you for your reply, Mike, I'm agree, it's more logical (personally I've not a great experience/feeling with algebraic calculators), but usually, having to choose the first answer I give to myself is not the good one , maybe there is another reason more "official", as you wrote

[Guenter Schink]

(04-30-2021 08:04 PM)aurelio Wrote:  Excuse me for my trivial question, but how happened that the function (calculated by an internal routine) y^x changed starting from the HP45 after to has been, on the HP35, x^y ?

There is a Museum somewhere they have an explanation.

Quote:The 35 is well-known for having an x^y key instead of y^x. This makes a lot of sense on the 35 since it didn't have a 10x key. If you wanted the anti-log of a number in x, you entered 10 x^y.

Günter

[aurelio]

[quote='Guenter Schink' pid='147130' dateline='1619815752']
There is a Museum somewhere they have an explanation.

Quote:

Shame on me , I missed it completely, my first calculator was the 25c thank-you Günter

[Dave Britten]

Interestingly, x^y makes it easier to calculate a sequence of powers, since you go from the "top" downward.

e.g.: 2^2^2^2 = 2^(2^(2^2))

On a 35: 2 ENTER 2 x^y 2 x^y 2 x^y

On a 45: 2 ENTER 2 y^x 2 x><y y^x 2 x><y y^x

Yes, I know there are other ways to do this specific example (fill the stack with 2, etc.), but you get the idea.

[aurelio]

Shame twice on me, I wrote "starting from the HP45", forgetting that the second pocket calculator, made by HP has been the HP80, not scientific, but anyway equipped with the y"x key

[aurelio]

I've found here another previous old discussion very interesting about that key....

[EdS2]

Oh - that is interesting - a negative zero value!