AB∥DE且BC∥EF．证明：∵六边形ABCDEF的内角都相等，∴∠FAB=∠B=∠C=∠CDE=∠E=∠F=120°，又∵∠DAB=60°，∴∠FAD=∠DAB=60°，∴∠F+∠FAD=∠B+∠DAB=180°，∴BC∥AD，EF∥AD，∴BC∥EF．∵BC∥AD，∠C=120°...