Relationships? Hmm...

[RZ923]

I found cyclic quadrilaterals

Quite similar to the Day 12 quadrilateral.

The are both quadrilaterals (obviously),

• the cyclic quadrilateral has opposite sides angles up to the same thing ($180^{\circ}$)
• and the new quadrilateral has opposite sides sum up to the same thing
  and they are all related to circles.
  Hmm...interesting.

[RZ923]

Wait are they actually the same thing?!