Example: congruence modulo 2 is an equivalence relation For any xEZ, or x=0 mod 2,or x=I mod 2, le or x∈E,orx∈O. AndE∩O= E and o RE, O is a partition of ZExample：congruence modulo 2 is an equivalence relation. For any xZ, or x=0 mod 2,or x=1 mod 2, i.e or xE ,or xO. And E∩O= E and O， {E, O} is a partition of Z