Mathematics for IGCSE & O level - Circle Theorems (Section 2 - No. 48)

Which properties must be true in a cyclic quadrilateral?

All angles must be acute.

Opposite angles must add up to 180 degrees.

All sides must be of equal length.

The diagonals bisect each other.

A cyclic quadrilateral is a quadrilateral whose vertices all lie on a single circle. Its opposite angles must add up to 180 degrees.