Tiling the Plane

Drag the blue points above to form different kinds of quadrilaterals. How many different quadrilaterals can you make?

What patterns do you notice? What conjecture(s) can you make about quadrilaterals tiling the plane?

Try to prove your conjecture(s), or explain your reasoning for why they might be true. The following lemma may be helpful: The sum of the interior angles of a quadrilateral is .