
theorem
for X be RealNormSpace, x be Element of REAL, v be Point of RNS_Real
  st x=v holds -x = -v
proof
   let X be RealNormSpace, x be Element of REAL, v be Point of RNS_Real;
   assume x=v; then
   (-1)*x = (-1)*v by BINOP_2:def 11;
   hence thesis by RLVECT_1:16;
end;
