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Gary,

The discussion you refer to was very interesting and the conclusion came to the same result of the operations of the Bygrave in use whichever way you looked at it; but I remember being personally convinced it was not the conventional received wisdom of logCosine and logCoTangent scales even though this might constitute heresy here. I still think this has been perpetuated because the original text refers to Tangent and Cosine in the formulae.

The interesting thing about the Bygrave application of the formulae on the slide rule itself is that in at least one of the operations (which I cannot now remember without looking into it all carefully again) of the actual slide rule manipulation (involving either multiply or divide) provides the opposite of that in the formulae - and this was because the scale was inverted, so it works out correctly. This was a very clever insight of Bygrave and is what makes the slide rule so simple to use and it 'works'.

Douglas Denny.
Chichester, England.
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