theorem Th28: :: JGRAPH_5:28

for P being non empty compact Subset of (TOP-REAL 2) st P = { q where q is Point of (TOP-REAL 2) : |.q.| = 1 } holds
( W-bound P = - 1 & E-bound P = 1 & S-bound P = - 1 & N-bound P = 1 )