(1) This contained work on planar and spherical trigonometry originally done much earlier in about 1464.(2) He worked on and off throughout his career on mathematical logic, no surprise for a student of Bernays, and he did some early work on planar graphs.(3) Clearly the centroid of the planar region surrounded by the polygon is at point A.(4) We are trying to connect the houses to the utilities as a planar graph.(5) The resulting graph is planar , that is can be drawn in the plane without any edges crossing.
