theorem Th7: :: GOBRD13:14

for i1, i2, j1, j2 being Nat
for G1, G2 being Go-board st G1 * ((i1 -' 1),j1) in Values G2 & 1 < i1 & i1 <= len G1 & 1 <= j1 & j1 <= width G1 & 1 < i2 & i2 <= len G2 & 1 <= j2 & j2 <= width G2 & G1 * (i1,j1) = G2 * (i2,j2) holds
(G1 * ((i1 -' 1),j1)) `1 <= (G2 * ((i2 -' 1),j2)) `1