let i, j, k be Nat; for f being V8() standard special_circular_sequence st 1 <= i & i + 1 < len (GoB f) & 1 <= j & j <= width (GoB f) & 1 <= k & k + 1 < len f & LSeg (((GoB f) * ((i + 1),j)),((GoB f) * ((i + 2),j))) = LSeg (f,k) & LSeg (((GoB f) * (i,j)),((GoB f) * ((i + 1),j))) = LSeg (f,(k + 1)) holds
( f /. k = (GoB f) * ((i + 2),j) & f /. (k + 1) = (GoB f) * ((i + 1),j) & f /. (k + 2) = (GoB f) * (i,j) )
let f be V8() standard special_circular_sequence; ( 1 <= i & i + 1 < len (GoB f) & 1 <= j & j <= width (GoB f) & 1 <= k & k + 1 < len f & LSeg (((GoB f) * ((i + 1),j)),((GoB f) * ((i + 2),j))) = LSeg (f,k) & LSeg (((GoB f) * (i,j)),((GoB f) * ((i + 1),j))) = LSeg (f,(k + 1)) implies ( f /. k = (GoB f) * ((i + 2),j) & f /. (k + 1) = (GoB f) * ((i + 1),j) & f /. (k + 2) = (GoB f) * (i,j) ) )
assume that
A1:
1 <= i
and
A2:
i + 1 < len (GoB f)
and
A3:
( 1 <= j & j <= width (GoB f) )
and
A4:
1 <= k
and
A5:
k + 1 < len f
and
A6:
LSeg (((GoB f) * ((i + 1),j)),((GoB f) * ((i + 2),j))) = LSeg (f,k)
and
A7:
LSeg (((GoB f) * (i,j)),((GoB f) * ((i + 1),j))) = LSeg (f,(k + 1))
; ( f /. k = (GoB f) * ((i + 2),j) & f /. (k + 1) = (GoB f) * ((i + 1),j) & f /. (k + 2) = (GoB f) * (i,j) )
A8:
i < i + 2
by XREAL_1:29;
i + (1 + 1) = (i + 1) + 1
;
then
i + 2 <= len (GoB f)
by A2, NAT_1:13;
then A9:
((GoB f) * (i,j)) `1 < ((GoB f) * ((i + 2),j)) `1
by A1, A3, A8, GOBOARD5:3;
A10:
1 <= k + 1
by NAT_1:11;
A11:
k + (1 + 1) = (k + 1) + 1
;
then
k + 2 <= len f
by A5, NAT_1:13;
then A12:
LSeg (((GoB f) * (i,j)),((GoB f) * ((i + 1),j))) = LSeg ((f /. (k + 1)),(f /. (k + 2)))
by A7, A11, A10, TOPREAL1:def 3;
then A13:
( ( (GoB f) * (i,j) = f /. (k + 2) & (GoB f) * ((i + 1),j) = f /. (k + 1) ) or ( (GoB f) * (i,j) = f /. (k + 1) & (GoB f) * ((i + 1),j) = f /. (k + 2) ) )
by SPPOL_1:8;
A14:
LSeg (((GoB f) * ((i + 1),j)),((GoB f) * ((i + 2),j))) = LSeg ((f /. k),(f /. (k + 1)))
by A4, A5, A6, TOPREAL1:def 3;
then
( ( (GoB f) * ((i + 1),j) = f /. (k + 1) & (GoB f) * ((i + 2),j) = f /. k ) or ( (GoB f) * ((i + 1),j) = f /. k & (GoB f) * ((i + 2),j) = f /. (k + 1) ) )
by SPPOL_1:8;
hence
f /. k = (GoB f) * ((i + 2),j)
by A12, A9, SPPOL_1:8; ( f /. (k + 1) = (GoB f) * ((i + 1),j) & f /. (k + 2) = (GoB f) * (i,j) )
thus
f /. (k + 1) = (GoB f) * ((i + 1),j)
by A14, A13, A9, SPPOL_1:8; f /. (k + 2) = (GoB f) * (i,j)
thus
f /. (k + 2) = (GoB f) * (i,j)
by A14, A13, A9, SPPOL_1:8; verum