Sum of angles of a triangle The relation between angular defect and the triangle's area was first proven by Johann Heinrich Lambert. One can easily see how hyperbolic geometry breaks Playfair's axiom, Proclus' axiom (the parallelism, defined as non-intersection, is intransitive in an hyperbolic plane), the equidistance postulate (the points on one side of, and equidistant from, a given line do not form a line), and Pythagoras' theorem. A circle cannot have arbitrarily small curvature, so the three points property also fails. The sum of the angles can be arbitrarily small (but positive). For an ideal triangle, a generalization of hyperbolic triangles, this sum is equal
Utah teapot several books and computer graphic journals. The Utah teapot sometimes appears in the "Pipes" screensaver shipped with Microsoft Windows, but only in versions prior to Windows XP, and has been included in the "polyhedra" XScreenSaver hack since 2008. Jim Blinn (in one of his "Project MATHEMATICS!" videos) proves an amusing (but trivial) version of the Pythagorean theorem: Construct a (2D) teapot on each side of a right triangle and the area of the teapot on the hypotenuse is equal to the sum of the areas of the teapots on the other two sides. Loren Carpenter's 1980 CGI film "Vol Libre"