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