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George,

Thank you.



You wrote:

> My 2-volume edition of Bowditch (vol.2 is 1981) states and derives all
> three expressions. In vol 2 it's in "part 3, Navigational calculations", in
> chapter 7, "Calculations of Celestial Navigation", paras 707-710.


My Bowditch is the 1995 edition and the nearest comparable material that
I can find is in para 2205. That gives the cosine and tangent
expressions (not the sine) but does not explain the derivation of either
of them. (Nor does it show how the formula for altitude is derived.)

Maybe my 1955 edition of the Admiralty Manual of Navigation (Vol.III)
will explain it all -- when I can make time to slowly work through that
and the two preceding volumes.


Trevor Kenchington


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