reserve m,k,j,j1,i,i1,i2,n for Nat,
  r,s for Real,
  C for compact non vertical non horizontal Subset of TOP-REAL 2,
  G for Go-board,
  p for Point of TOP-REAL 2;

theorem Th50:
  1 <= X-SpanStart(C,n)-'1 & X-SpanStart(C,n)-'1 < len Gauge(C,n)
proof
  2 < X-SpanStart(C,n) by Th49;
  then
A1: X-SpanStart(C,n)-'1+1 = X-SpanStart(C,n) by XREAL_1:235,XXREAL_0:2;
  1 < X-SpanStart(C,n) by Th49,XXREAL_0:2;
  hence 1 <= X-SpanStart(C,n)-'1 by A1,NAT_1:13;
  X-SpanStart(C,n) < len Gauge(C,n) & X-SpanStart(C,n)-'1 <= X-SpanStart(C
  ,n) by Th49,NAT_D:44;
  hence thesis by XXREAL_0:2;
end;
