reserve i,j,k,k1,k2,i1,i2,j1,j2 for Nat,
  r,s for Real,
  x for set,
  f for non constant standard special_circular_sequence;

theorem Th8:
  ex i,j st i<=len GoB f & j<=width GoB f & Int cell(GoB f,i,j) c=
  LeftComp f \/ RightComp f
proof
  1+1<=len f by GOBOARD7:34,XXREAL_0:2;
  then
A1: (ex i,j st i <= len GoB f & j <= width GoB f & cell(GoB f,i,j) =
  left_cell( f,1) )& Int left_cell(f,1) c= LeftComp f by GOBOARD9:11,21;
  LeftComp f c= LeftComp f \/ RightComp f by XBOOLE_1:7;
  hence thesis by A1,XBOOLE_1:1;
end;
