let i, j be Element of NAT ; :: thesis: for G being Go-board st i < len G & 1 <= j & j < width G holds
LSeg (G * (i + 1),j),(G * (i + 1),(j + 1)) c= cell G,i,j
let G be Go-board; :: thesis: ( i < len G & 1 <= j & j < width G implies LSeg (G * (i + 1),j),(G * (i + 1),(j + 1)) c= cell G,i,j )
assume that
A1: i < len G and
A2: ( 1 <= j & j < width G ) ; :: thesis: LSeg (G * (i + 1),j),(G * (i + 1),(j + 1)) c= cell G,i,j
A3: LSeg (G * (i + 1),j),(G * (i + 1),(j + 1)) c= v_strip G,i by A1, A2, Th14;
( 1 <= i + 1 & i + 1 <= len G & j + 1 <= width G ) by A1, A2, NAT_1:11, NAT_1:13;
then LSeg (G * (i + 1),j),(G * (i + 1),(j + 1)) c= h_strip G,j by A2, Th18;
hence LSeg (G * (i + 1),j),(G * (i + 1),(j + 1)) c= cell G,i,j by A3, XBOOLE_1:19; :: thesis: verum