reserve a,b,c,v,v1,x,y for object;
reserve V,A for set;
reserve d for TypeSCNominativeData of V,A;

theorem Th3:
  for a,b,c,d,e,f being object holds rng {[a,b],[c,d],[e,f]} = {b,d,f}
  proof
    let a,b,c,d,e,f be object;
A1: rng {[a,b],[c,d]} = {b,d} by RELAT_1:10;
A2: rng {[e,f]} = {f} by RELAT_1:9;
    {[a,b],[c,d],[e,f]} = {[a,b],[c,d]} \/ {[e,f]} by ENUMSET1:3;
    hence rng {[a,b],[c,d],[e,f]} = rng {[a,b],[c,d]} \/ rng {[e,f]}
    by XTUPLE_0:27
    .= {b,d,f} by A1,A2,ENUMSET1:3;
  end;
