Points c,a,b are connected to form a triangle along the surface of a sphere. Points R,E,N are connected to form a triangle on a euclidean.
What is true between spherical and euclidean geometry?
holy smoke! Where to start?
The angles on a spherical triangle sum to more than 180, vs 180 in the plane.
pick up any text on spherical trig and you can easily list a dozen things right off the bat.