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The square root of ten revisited - Palmer O. Hanson, Jr. - 03-26-2010
In response to Gene Wright's "Happy Square Root of 10 day!" (16 March) I wrote: Quote:Stan Keeley and Martin Pinckney reported that the Hemmi 250 has the CF and DF scales folded at the square root of ten. I have a Hemmi 250 in my collection.
Page 38 of Quote:The CF and DF scales on my K&E 4094 Merchant's Mannheim, K&E 4095 Merchant's Duplex, and K&E GP12 Business-Science slide rules all have the CF and DF scales folded at pi. In my collection only my A.W.Faber-Castell 67/22R Business slide rule does have the CF and DF scales folded at 3.6 .
I can't recall needing the square root of ten in any of my calculations. Is there a technology where the square root of ten apprears frequently in calculations?
Re: The square root of ten revisited - BobVA - 03-28-2010
I've got a guess. The wikipedia article below says there are two uses for the CF and DF scales. Besides convenience for calculations involving pi, it also recommends use in lieu of the C/D scales when it isn't obvious which index on the latter to use in order to keep the results on scale. I hadn't heard of this trick, but it makes sense. So, if the folded scale was originally devised to solve the "index ambiguity" problem, it would have been logical to fold the scale in the middle (10^0.5). Then perhaps some other clever person came along and noted that you could do the same thing by folding the scale at the nearly equivalent value of pi, with the bonus of adding the pi computation features.
Just speculation, of course. Wikipedia Slide Rule Article - "other operations"
Re: The square root of ten revisited - Martin Pinckney - 03-28-2010
Quote:I think you hit on it! |