reserve n,i,j,k,l for Nat;
reserve D for non empty set;
reserve c,d for Element of D;
reserve p,q,q9,r for FinSequence of D;
reserve RAS for MidSp-like non empty ReperAlgebraStr over n+2;
reserve a,b,d,pii,p9i for Point of RAS;
reserve p,q for Tuple of (n+1),RAS;
reserve m for Nat of n;

theorem Th8:
  i<=n implies i+1 is Nat of n
proof
  assume i<=n;
  then
A1: i+1<=n+1 by XREAL_1:7;
  1<=i+1 by NAT_1:11;
  hence thesis by A1,Def2;
end;
