reserve A,B for Ordinal,
        o for object,
        x,y,z for Surreal,
        n for Nat,
        r,r1,r2 for Real;

theorem Th38:
   x == 0_No implies |. -x .| == |.x.|
proof
  assume
A1: x==0_No;
  then -x == - 0_No=0_No by SURREALR:10;
  then |.-x.| ==0_No  & |.x.| == 0_No by A1,Def6;
  hence thesis by SURREALO:4;
end;
