Hey im reading "The Road to Reality" and I'm trying to get a grasp on hyperbolic Geometry. One thing that i wasn't really sure about was how do you measure the curved angles (i.e. when there is a triangle that's formed by the hyperbolic "circular arc" lines how do you find the angle between those two "lines" would you just take the tangent and use that slope to determine it as if it were a straight line)? Also in the book they say that the distance between two points is the log (QA*PB)/(QB*PA), where does this come from? and if that is the distance between two points then how would you find the original distances (QA, PB ect) to plug in for the formula? Also any good websites on the subject would help.