reserve            S for satisfying_CongruenceSymmetry
                         satisfying_CongruenceEquivalenceRelation
                         TarskiGeometryStruct,
         a,b,c,d,e,f for POINT of S;

theorem Satz2p3: ::GTARSKI1:12 ::EquivTransitive
  a,b equiv c,d & c,d equiv e,f implies a,b equiv e,f
  proof
    assume
A1: a,b equiv c,d & c,d equiv e,f;
    then c,d equiv a,b by Satz2p2;
    hence thesis by A1,GTARSKI1:def 6;
  end;
