Circle Limit 4 -- Heaven and Hell by M.C.Escher 1960

Escher's work represents a projection of creatures "living" in a 2-dimensional space, which may or may not be flat, onto the page, which is definitely flat. The creatures are all the same size in their own world - the apparent change in size of the angels and devils in Heaven and Hell is an artifact of the projection onto the flat page, like the distortion of the size of Greenland on a Mercator map in an atlas.

1. Pick an angel and label the tip of the angel's feet, and the 2 tips of her wings. Figure out the angle at each of these 3 points by taking 360 degrees and dividing by the total number of angels and devils that meet at that point. For example, at the feet coming into the center of the disk, there are 6 angels and devils coming into that point and so the angle at that point is 360/6 = 60 degrees. What is the sum of the 3 angles? Is Escher's representation a geometry which satisfies the Euclidean geometry laws that you learned in high school?
2. Lines should preserve symmetry (mirror reflections), so use this idea to draw some "lines" in this space. Start by drawing mirror "lines" through the center of an angel and continue these mirrors. Draw at least 4 "lines". Is Playfair's Postulate (given a line and a point off the line there is exactly one parallel) true in this space?