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I was responsible for diverting this discussion into Ptolemy's grasp of
trig. around AD 150. So apologies to anyone who is outraged by taking
matters so far away from the practical problems of navigation.

Herbert Prinz responded.

>Trying hard to give the appearance that what we are discussing here has
>anything
>to do with navigation, I shall mention in passing the name of Cotter. (I know,
>George, that you maintain this list...)
>
>In A History etc., p.16 he writes that "Ptolemy had the theorem
>
>    "sin(A+B) = sin(A)cos(B) + cos(A)sin(B)
>
>"This theorem is usually known as Ptolemean Theorem."
>
>Now that you have seen the relevant chapter in the Almagest, would you agree
>with this?

==================

My perspicacity is less than Herbert rates it. All I have done, so far, is
to dip into Ptolemy.

I probably wouldn't recognise "Ptolemy's theorem" if it said "hello" to me.
Presumably, it would have to be expressed in different terms to the
equation Cotter gave, as Ptolemy doesn't seem to have cosines, as such,
within his grasp.

So I can't answer Herbert's question, but it would be interesting to
discover his own view of that matter.

George.

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