A Community Devoted to the Preservation and Practice of Celestial Navigation and Other Methods of Traditional Wayfinding
From: Sean C
Date: 2021 Feb 14, 22:14 -0800
The proof is given on page 261 (Chapter 16, §1601) of the 2002 edition of Bowditch. I have also attached my rendering of it below.
Of course, I understand if you still want to work it out for yourself. In that case: don't look at the attached picture. ;)