Re: The square root of ten revisited Message #2 Posted by BobVA on 28 Mar 2010, 2:47 p.m., in response to message #1 by Palmer O. Hanson, Jr.
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"
Edited: 28 Mar 2010, 3:09 p.m.
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