Definition of Cyclic quadrilateral

What is Cyclic Quadrilateral? State Some properties of Cyclic quadrilateral?

The quadrilateral formed by angle bisectors of a cyclic quadrilateral is also cyclic.

The quadrilateral formed by angle bisectors of a cyclic quadrilateral is also cyclic.

If the diagonals of a cyclic quadrilateral intersect at the centre of a circle , then the quadrilateral is "_______________" .

If diagonals of a cyclic quadrilateral are diameters of the circle through the vertices of the quadrilateral,prove that it is a rectangle

If diagonals of a cyclic quadrilateral are diameters of the circle through the vertices of the quadrilateral,prove that it is a rectangle.