|Re: HP calcs with X^Y function|
Message #7 Posted by Vieira, Luiz C. (Brazil) on 21 Jan 2002, 12:09 a.m.,
in response to message #5 by mapet
This is something I did not notice so far. Yes, I agree with Thibaut: the HP35 was the first - and the only - pocket RPN with x^y. All others offered [y^x] function (and label) to agree with other non-commutative math operations, i.e.: /, -, %. (Please, if the term commutative is not used this way, forgive-me and help me placing the correct one.) Say, 4-7 is not equal to 7-4, while 4+7 is equal to 7+4 (mathematical results). Raising to a power is non-commutative. Let's take this: at the moment we need 4-3, the sequence 4 ENTER 3 [-] will give the expected result; what about 4^3? We would place 4 ENTER 3 [y^x]; if there is a [x^y] function, the sequence should be 3 ENTER 4 [x^y] (remember, x and y reffer to stack-registers X and Y).
The algebraics differ for the math sequence: 4 [x^y] 3 [=] works fine, as 4 [y^x] 3 [=] is confusing for those already familiar with algebraic notation.
With RPN models, the input sequence will really dictate who will be raised to who, but [y^x] will always mean [y-contents ^ x-contents]. In the new ones, y- meaning level 2 argument, and x- meaning level 1 argument. With the 49G, the [y^x} key adds a single [^] character, algebraic or RPN mode.