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    Re: Spherical Law of Cosines
    From: Dan Allen
    Date: 2002 Oct 18, 14:44 -0700

    Thanks to Bill Arden who pointed out yet another mistake of mine...
    I have been writing these things while being very involved in other
    matters and my memory has not been what it used to be...
    sin(c) = sin(a)*sin(b) + cos(a)*cos(b)*cos(ab)
    is what I should have written as the alternative version.
    With apologies,
    Begin forwarded message:
    > From: ARDENW714@aol.com
    > Date: Fri Oct 18, 2002  12:22:00 PM US/Pacific
    > To: danallen46@ATTBI.COM
    > Subject: law of cosines
    > Hi, Dan -
    > You wrote recently ...
    > "Note too that there are equivalent ways of writing the spherical law
    > of cosines.  One can write it as
    > cos(c) = sin(a)*sin(b) + cos(a)*cos(b)*cos(ab)
    > where the pairs of sin/cos of a/b are switched."
    > Isn't the left side of that equation SIN(c)? Or is that another
    > substitution that I didn't know enough to make?
    > I hope I haven't been doing that wrong - I've been using
    > sin(Hc) = sin(lat)*sin(dec) + cos(lat)*cos(dec)*cos(LHA) and it seems
    > to work correctly.
    > Regards,
    > Bill Arden

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