theorem :: JORDAN9:18

for i, j being Nat
for G being Go-board st 1 <= i & i + 1 <= len G & 1 <= j & j + 1 <= width G holds
cell (G,i,j) = { |[r,s]| where r, s is Real : ( (G * (i,j)) `1 <= r & r <= (G * ((i + 1),j)) `1 & (G * (i,j)) `2 <= s & s <= (G * (i,(j + 1))) `2 ) }