### Video Transcript

Is π΄π΅πΆπ· a cyclic quadrilateral?

Letβs recall that a cyclic quadrilateral is a four-sided polygon whose vertices are inscribed on a circle. We can prove that a quadrilateral is cyclic or not by using a few different properties. However, we can observe in π΄π΅πΆπ· that weβre given the diagonals. If an angle created by a diagonal and side is equal in measure to the angle created by the other diagonal and opposite side, then the quadrilateral is cyclic. If these angle measures are not equal, then it is not a cyclic quadrilateral.

So, letβs look at this angle πΆπ·π΅. Itβs an angle created by a diagonal and a side. The angle created by the other diagonal and opposite side would be this angle πΆπ΄π΅. And of course 82 degrees is not equal to 78 degrees. Therefore, the measure of angle πΆπ·π΅ is not equal to the measure of angle πΆπ΄π΅.

We can then give the answer no, since π΄π΅πΆπ· is not a cyclic quadrilateral.