theorem
for
i,
j being
Nat for
G being
Go-board st 1
<= i &
i < len G & 1
<= j &
j + 1
< width G holds
LSeg (
((1 / 2) * ((G * (i,j)) + (G * ((i + 1),(j + 1))))),
((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 2))))))
c= ((Int (cell (G,i,j))) \/ (Int (cell (G,i,(j + 1))))) \/ {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))}