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

theorem
for f be PartFunc of REAL m,REAL n, x be Element of REAL m
  st f is_continuous_in x holds -f is_continuous_in x
proof
   let f be PartFunc of REAL m,REAL n, x be Element of REAL m;
   assume f is_continuous_in x; then
   (-1)(#)f is_continuous_in x by Th30;
   hence thesis by NFCONT_4:7;
end;
