Hey @BullyBear The sum of 180 degrees for the three internal angles of a triangle is true only in planar of Euclidian geometry. Other types of geometry are referred to as non-Euclidian; here is a useful starting point for reading: https://en.wikipedia.org/wiki/Non-Euclidean_geometry
As the Earth is nearly a sphere (though somewhat squashed at the poles, and a bit pear-shaped also but in a very minor way), spherical geometry is useful when considering lines and angles on the surface of the Earth
good luck in your inquiries, thinking and adventures in this space!
PS Also look up "great circle routes" when considering shortest distance between two point son the globe
