theorem Th38:
  Class(RI,0.X) c= I
proof
  let x be object;
  assume
A1: x in Class(RI,0.X);
  then consider y being object such that
A2: [y,x] in RI and
A3: y in {0.X} by RELAT_1:def 13;
  reconsider x as Element of X by A1;
  reconsider y as Element of X by A3,TARSKI:def 1;
  y=0.X by A3,TARSKI:def 1;
  then x\0.X in I by A2,Def12;
  hence thesis by BCIALG_1:2;
end;
