theorem Th8: :: GOBOARD1:15

for n, m, i, k being Nat
for G being Go-board st i in Seg (width G) & width G = m + 1 & m > 0 & n in dom G & 1 <= k & k < i holds
( (DelCol (G,i)) * (n,k) = G * (n,k) & k in Seg (width G) ) by MATRIX_0:69;