theorem Th118: :: GLIB_012:118

for G1 being _Graph
for G2 being GraphComplement of G1
for v1 being Vertex of G1
for v2 being Vertex of G2 st v1 = v2 holds
v2 .allNeighbors() = (the_Vertices_of G2) \ ((v1 .allNeighbors()) \/ {v2})