reserve m,n for non zero Element of NAT;
reserve i,j,k for Element of NAT;
reserve Z for set;

theorem
for f,g be PartFunc of REAL m,REAL n st
  f is_continuous_on Z holds -f is_continuous_on Z
proof
   let f,g be PartFunc of REAL m,REAL n;
   assume A1: f is_continuous_on Z;
   (-1)(#)f is_continuous_on Z by A1,Th34;
   hence thesis by NFCONT_4:7;
end;
