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Re: Cosine formula to solve a right spherical triangle?
From: David Iwancio
Date: 2020 Jan 21, 10:27 -0800
From: David Iwancio
Date: 2020 Jan 21, 10:27 -0800
The Law of Cosines and Napier's Analogies are the same thing. The analogies are what's left over after accounting for cos(X) = sin(90°-X) and for cos(90°) = 0
cos(C) = cos(A)*cos(B) + sin(A)*sin(B)*cos(γ)
cos(C) = cos(A)*cos(B) + sin(A)*sin(B)*cos(90°)
cos(C) = cos(A)*cos(B) + sin(A)*sin(B)*0
cos(C) = cos(A)*cos(B) + 0
cos(C) = cos(A)*cos(B)
sin(90°-C) = cos(A)*cos(B)
