theorem :: GOBRD13:42

for k, n being Nat
for f being FinSequence of (TOP-REAL 2)
for G being Go-board st 1 <= k & k + 1 <= len f & f is_sequence_on G & k + 1 <= n holds
( front_left_cell (f,k,G) = front_left_cell ((f | n),k,G) & front_right_cell (f,k,G) = front_right_cell ((f | n),k,G) )