NavList:
A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
Re: Spherical Law of Cosines
From: Dan Allen
Date: 2002 Oct 18, 14:44 -0700
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, Dan 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 >