reserve n,m,i,k for Element of NAT;
reserve x,X,X1 for set;
reserve r,p for Real;
reserve s,x0,x1,x2 for Real;
reserve f,f1,f2 for PartFunc of REAL,REAL n;
reserve h for PartFunc of REAL,REAL-NS n;
reserve W for non empty set;

theorem
  (ex N be Neighbourhood of x0 st dom f /\ N = {x0}) implies
  f is_continuous_in x0
  proof
    given N be Neighbourhood of x0 such that
A1: dom f /\ N = {x0};
    reconsider g = f as PartFunc of REAL,REAL-NS n
      by REAL_NS1:def 4;
    g is_continuous_in x0 by A1,NFCONT_3:11;
    hence thesis;
  end;
