 reserve G, A for Group;
 reserve phi for Homomorphism of A,AutGroup(G);
 reserve G, A for Group;
 reserve phi for Homomorphism of A,AutGroup(G);
reserve G1,G2 for Group;

theorem :: TH116
  center Dihedral_group 1 = Dihedral_group 1
    by ThD1Commutative, GROUP_5:82;
