theorem Th17: :: GOBOARD5:17

for i, j being Nat
for G being Matrix of (TOP-REAL 2) st G is Y_equal-in-column & G is Y_increasing-in-line & 1 <= i & i <= len G & 1 <= j & j + 1 <= width G holds
LSeg ((G * (i,j)),(G * (i,(j + 1)))) c= h_strip (G,j)