Figure 8
(a) A planar finite unit-distance graph with edges of unequal length; (b) the unit-distance graph in (a) now equalized; (c) the unit-distance graph in (b) in which vertex 2 is moved out of the plane of the page and vertex 5 is moved into the plane of the page to produce a non-planar unit-distance graph; (d) the unit-distance graph in (b) in which vertices 2 and 5 are moved such that the T⋯T separation 2–5 (denoted by the red ellipse) is shorter than the T–T distance and is not allowed. |