A couple of days ago I wrote a post on what, and how to find, the cosine rule on a sphere. In this post I’ll show you the sine rule on a sphere.

## Cosine Rule on a Sphere

As all (well, at least those that can remember) 15+ year old’s know, to find the length of a side of a non-right angled triangle you can’t use Pythagoras theorem and instead require the so called ‘Cosine Rule’.