Look at the parallelogram ABCD. The slopes of the sides are marked with letters m. Drag all vertices around and observe which elements change and which elements stay the same. Based on your observation, think about how can you define a parallelogram?

Look at the parallelogram EFHG. The measures of the sides are shown.[br] Drag all vertices around and observe which elements change [br]and which elements stay the same. Based on your observation, think about[br] how can you define a parallelogram? (This definition should be different from your first definition)

Look at the parallelogram IJLK. The measures of the angles are shown. [br] Drag all vertices around and observe which elements change [br]and which elements stay the same. Based on your observation, think about[br] how can you define a parallelogram? (This definition should be different from your first and second definition)

Look at the parallelogram POMN. The measures of the parts of the diagonals are shown. [br] Drag all vertices around and observe which elements change [br]and which elements stay the same. Based on your observation, think about[br] how can you define a parallelogram? Can you think about one more definition which is different from your previous three?