reserve a,b,p,k,l,m,n,s,h,i,j,t,i1,i2 for natural Number;

theorem Th36:
  n-'i=0 implies n<=i
proof
  assume
A1: n-'i=0;
  assume i<n;
  then i+1<=n by NAT_1:13;
  then i+1-i<=n-i by XREAL_1:9;
  hence contradiction by A1,XREAL_0:def 2;
end;
