 reserve X, Y for set, A for Ordinal;
 reserve z,z1,z2 for Complex;
 reserve r,r1,r2 for Real;
 reserve q,q1,q2 for Rational;
 reserve i,i1,i2 for Integer;
 reserve n,n1,n2 for Nat;

theorem
  multRel(INT,i1) * multRel(INT,i2) = multRel(INT,i1*i2)
proof
  A1: multRel(INT,i1) * multRel(INT,i2) c= multRel(INT,i1*i2) by Th51;
  now
    let x,y be object;
    reconsider a=x,b=y as set by TARSKI:1;
    assume A2: [x,y] in multRel(INT,i1*i2);
    then [a,b] in multRel(INT,i1*i2);
    then A3: a in INT & b in INT by MMLQUER2:4;
    then reconsider a,b as Integer;
    A4: b = i1 * i2 * a by A2, Th42;
    set c = i1 * a;
    c in INT & b = i2 * c by A4, INT_1:def 2;
    then [a,c] in multRel(INT,i1) & [c,b] in multRel(INT,i2) by A3, Th42;
    hence [x,y] in multRel(INT,i1) * multRel(INT,i2) by RELAT_1:def 8;
  end;
  then multRel(INT,i1*i2) c= multRel(INT,i1) * multRel(INT,i2)
    by RELAT_1:def 3;
  hence thesis by A1, XBOOLE_0:def 10;
end;
