reserve a, b for Real;
reserve RNS for RealNormSpace;
reserve x, y, z, g, g1, g2 for Point of RNS;

theorem Th2:
  ||.-x.|| = ||.x.||
proof
A1: |.-1.| = -(-1) by ABSVALUE:def 1
    .= 1;
  ||.-x.|| = ||.(-1) * x.|| by RLVECT_1:16
    .= |.-1.| * ||.x.|| by Def1;
  hence thesis by A1;
end;
