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

let G be Go-board; :: thesis: ( 1 <= i & i < len G & 1 <= j & j < width G implies LSeg (((1 / 2) * ((G * (i,j)) + (G * ((i + 1),(j + 1))))),((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))) c= (Int (cell (G,i,j))) \/ {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))} )
assume that
A1: 1 <= i and
A2: i < len G and
A3: 1 <= j and
A4: j < width G ; :: thesis: LSeg (((1 / 2) * ((G * (i,j)) + (G * ((i + 1),(j + 1))))),((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))) c= (Int (cell (G,i,j))) \/ {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))}
let x be object ; :: according to TARSKI:def 3 :: thesis: ( not x in LSeg (((1 / 2) * ((G * (i,j)) + (G * ((i + 1),(j + 1))))),((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))) or x in (Int (cell (G,i,j))) \/ {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))} )
assume A5: x in LSeg (((1 / 2) * ((G * (i,j)) + (G * ((i + 1),(j + 1))))),((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))) ; :: thesis: x in (Int (cell (G,i,j))) \/ {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))}
then reconsider p = x as Point of (TOP-REAL 2) ;
consider r being Real such that
A6: p = ((1 - r) * ((1 / 2) * ((G * (i,j)) + (G * ((i + 1),(j + 1)))))) + (r * ((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))) and
A7: 0 <= r and
A8: r <= 1 by A5;
now :: thesis: ( ( r = 1 & p in {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))} ) or ( r < 1 & p in Int (cell (G,i,j)) ) )
per cases ( r = 1 or r < 1 ) by A8, XXREAL_0:1;
case r = 1 ; :: thesis: p in {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))}
then p = (0. (TOP-REAL 2)) + (1 * ((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))) by A6, RLVECT_1:10
.= 1 * ((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1))))) by RLVECT_1:4
.= (1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))) by RLVECT_1:def 8 ;
hence p in {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))} by TARSKI:def 1; :: thesis: verum
end;
case A9: r < 1 ; :: thesis: p in Int (cell (G,i,j))
set r3 = (1 - r) * (1 / 2);
set s3 = r * (1 / 2);
set r1 = (G * (i,1)) `1 ;
set r2 = (G * ((i + 1),1)) `1 ;
set s1 = (G * (1,j)) `2 ;
set s2 = (G * (1,(j + 1))) `2 ;
A10: (((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * (i,1)) `1))) + ((r * (1 / 2)) * (((G * (i,1)) `1) + ((G * (i,1)) `1))) = (G * (i,1)) `1 ;
0 <> width G by MATRIX_0:def 10;
then A11: 1 <= width G by NAT_1:14;
A12: i + 1 <= len G by A2, NAT_1:13;
i < i + 1 by XREAL_1:29;
then A13: (G * (i,1)) `1 < (G * ((i + 1),1)) `1 by A1, A12, A11, GOBOARD5:3;
then A14: ((G * (i,1)) `1) + ((G * (i,1)) `1) < ((G * (i,1)) `1) + ((G * ((i + 1),1)) `1) by XREAL_1:6;
then A15: (r * (1 / 2)) * (((G * (i,1)) `1) + ((G * (i,1)) `1)) <= (r * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)) by A7, XREAL_1:64;
1 - r > 0 by A9, XREAL_1:50;
then A16: (1 - r) * (1 / 2) > (1 / 2) * 0 by XREAL_1:68;
then ((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * (i,1)) `1)) < ((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)) by A14, XREAL_1:68;
then A17: (G * (i,1)) `1 < (((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))) + ((r * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))) by A15, A10, XREAL_1:8;
0 <> len G by MATRIX_0:def 10;
then A18: 1 <= len G by NAT_1:14;
A19: 1 <= i + 1 by A1, NAT_1:13;
((G * (i,1)) `1) + ((G * ((i + 1),1)) `1) < ((G * ((i + 1),1)) `1) + ((G * ((i + 1),1)) `1) by A13, XREAL_1:8;
then A20: (r * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)) <= (r * (1 / 2)) * (((G * ((i + 1),1)) `1) + ((G * ((i + 1),1)) `1)) by A7, XREAL_1:64;
A21: j + 1 <= width G by A4, NAT_1:13;
((G * (i,1)) `1) + ((G * ((i + 1),1)) `1) < ((G * ((i + 1),1)) `1) + ((G * ((i + 1),1)) `1) by A13, XREAL_1:6;
then A22: ((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)) < ((1 - r) * (1 / 2)) * (((G * ((i + 1),1)) `1) + ((G * ((i + 1),1)) `1)) by A16, XREAL_1:68;
(((1 - r) * (1 / 2)) * (((G * ((i + 1),1)) `1) + ((G * ((i + 1),1)) `1))) + ((r * (1 / 2)) * (((G * ((i + 1),1)) `1) + ((G * ((i + 1),1)) `1))) = (G * ((i + 1),1)) `1 ;
then A23: (((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))) + ((r * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))) < (G * ((i + 1),1)) `1 by A22, A20, XREAL_1:8;
A24: Int (cell (G,i,j)) = { |[r9,s9]| where r9, s9 is Real : ( (G * (i,1)) `1 < r9 & r9 < (G * ((i + 1),1)) `1 & (G * (1,j)) `2 < s9 & s9 < (G * (1,(j + 1))) `2 ) } by A1, A2, A3, A4, Th26;
A25: 1 <= j + 1 by A3, NAT_1:13;
j < j + 1 by XREAL_1:29;
then A26: (G * (1,j)) `2 < (G * (1,(j + 1))) `2 by A3, A21, A18, GOBOARD5:4;
then A27: ((G * (1,j)) `2) + ((G * (1,j)) `2) < ((G * (1,j)) `2) + ((G * (1,(j + 1))) `2) by XREAL_1:6;
A28: G * ((i + 1),(j + 1)) = |[((G * ((i + 1),(j + 1))) `1),((G * ((i + 1),(j + 1))) `2)]| by EUCLID:53
.= |[((G * ((i + 1),1)) `1),((G * ((i + 1),(j + 1))) `2)]| by A25, A21, A19, A12, GOBOARD5:2
.= |[((G * ((i + 1),1)) `1),((G * (1,(j + 1))) `2)]| by A25, A21, A19, A12, GOBOARD5:1 ;
((G * (1,j)) `2) + ((G * (1,(j + 1))) `2) < ((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2) by A26, XREAL_1:6;
then ((G * (1,j)) `2) + ((G * (1,j)) `2) < ((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2) by A27, XXREAL_0:2;
then A29: (r * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,j)) `2)) <= (r * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2)) by A7, XREAL_1:64;
A30: G * (i,j) = |[((G * (i,j)) `1),((G * (i,j)) `2)]| by EUCLID:53
.= |[((G * (i,1)) `1),((G * (i,j)) `2)]| by A1, A2, A3, A4, GOBOARD5:2
.= |[((G * (i,1)) `1),((G * (1,j)) `2)]| by A1, A2, A3, A4, GOBOARD5:1 ;
A31: (((1 - r) * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2))) + ((r * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2))) = (G * (1,(j + 1))) `2 ;
A32: G * (i,(j + 1)) = |[((G * (i,(j + 1))) `1),((G * (i,(j + 1))) `2)]| by EUCLID:53
.= |[((G * (i,1)) `1),((G * (i,(j + 1))) `2)]| by A1, A2, A25, A21, GOBOARD5:2
.= |[((G * (i,1)) `1),((G * (1,(j + 1))) `2)]| by A1, A2, A25, A21, GOBOARD5:1 ;
A33: (((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,j)) `2))) + ((r * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,j)) `2))) = (G * (1,j)) `2 ;
((G * (1,j)) `2) + ((G * (1,(j + 1))) `2) < ((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2) by A26, XREAL_1:6;
then ((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,(j + 1))) `2)) < ((1 - r) * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2)) by A16, XREAL_1:68;
then A34: (((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,(j + 1))) `2))) + ((r * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2))) < (G * (1,(j + 1))) `2 by A31, XREAL_1:8;
((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,j)) `2)) < ((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,(j + 1))) `2)) by A16, A27, XREAL_1:68;
then A35: (G * (1,j)) `2 < (((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,(j + 1))) `2))) + ((r * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2))) by A29, A33, XREAL_1:8;
p = (((1 - r) * (1 / 2)) * ((G * (i,j)) + (G * ((i + 1),(j + 1))))) + (r * ((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))) by A6, RLVECT_1:def 7
.= (((1 - r) * (1 / 2)) * ((G * (i,j)) + (G * ((i + 1),(j + 1))))) + ((r * (1 / 2)) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1))))) by RLVECT_1:def 7
.= (((1 - r) * (1 / 2)) * |[(((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)),(((G * (1,j)) `2) + ((G * (1,(j + 1))) `2))]|) + ((r * (1 / 2)) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1))))) by A30, A28, EUCLID:56
.= (((1 - r) * (1 / 2)) * |[(((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)),(((G * (1,j)) `2) + ((G * (1,(j + 1))) `2))]|) + ((r * (1 / 2)) * |[(((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)),(((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2))]|) by A28, A32, EUCLID:56
.= |[(((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))),(((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,(j + 1))) `2)))]| + ((r * (1 / 2)) * |[(((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)),(((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2))]|) by EUCLID:58
.= |[(((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))),(((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,(j + 1))) `2)))]| + |[((r * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))),((r * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2)))]| by EUCLID:58
.= |[((((1 - r) * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1))) + ((r * (1 / 2)) * (((G * (i,1)) `1) + ((G * ((i + 1),1)) `1)))),((((1 - r) * (1 / 2)) * (((G * (1,j)) `2) + ((G * (1,(j + 1))) `2))) + ((r * (1 / 2)) * (((G * (1,(j + 1))) `2) + ((G * (1,(j + 1))) `2))))]| by EUCLID:56 ;
hence p in Int (cell (G,i,j)) by A17, A23, A35, A34, A24; :: thesis: verum
end;
end;
end;
hence x in (Int (cell (G,i,j))) \/ {((1 / 2) * ((G * (i,(j + 1))) + (G * ((i + 1),(j + 1)))))} by XBOOLE_0:def 3; :: thesis: verum