Pythagoras, Pythagorean, Euclidean, Gravitational Lensing, Symmetry.
Figure 6). I named and measured the 3 angles with a protractor, obtaining the following values: α = 39° ± 1°, β =80° ± 1°, and gamma = 91°± 1°. Using the protractor on the globe surface was not easy, as you may appreciate in the pictures, and produced a quite big estimated uncertainty. Those