reserve r, s, t for Real;

theorem Th36: ::: SQUARE_1 or ABSVALUE
  |.r.| + |.s.| = 0 implies r = 0
proof
  set aa = |.r.|, ab = |.s.|;
A1: 0 <= aa & 0 <= ab by COMPLEX1:46;
  assume |.r.|+|.s.| = 0;
  then aa = 0 by A1;
  hence thesis by ABSVALUE:2;
end;
