The Museum of HP Calculators

HP Forum Archive 15

 logx yMessage #1 Posted by GWB on 10 June 2005, 10:33 p.m. Logarithm of y to base x ... There'll never be a logxy key; besides, it is not needed. But just for fun let's try to write a tiny program for this, the tiniest the best. On the 32Sii and the 33S only three steps will do the job. Anyone want to try? (logyx can be done in only four steps: LN x<>y LN /, but this entry order doesn't look so natural. However logxy in four steps is still possible on most calculators). Regards, Gerson.

 Re: logx yMessage #2 Posted by Tom Sherman on 12 June 2005, 10:19 a.m.,in response to message #1 by GWB Hi Gerson, Nice problem. Maybe this: (LN) (x root of y) (LN) or: (LOG) (x root of y) (LOG) Cheers, Tom

 BINGO! (Re: logx y)Message #3 Posted by GWB on 12 June 2005, 1:16 p.m.,in response to message #2 by Tom Sherman Hi Tom, Congratulations! Most likely you have made use of mathematical properties of logarithms to solve the problem. In fact, it can be shown that lny/lnx=ln(y^(1/lnx)). I must confess I found this out entirely by chance, playing with the 32Sii keyboard for a while. On the 33S my unorthodox method would have been even easier, as the [x xroot y] is not a shifted key :-) Thanks for your having appreciated the problem. For other HP scientific calcs (except the HP-35): [LN] [1/x] [y^x] [LN] Check this link out: Cheers, Gerson.

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