Prove that the quadrilateral formed (if possible) by the internal angle bisectors of any quadrilateral is cyclic.

Sum of all the interior angles of a quadrilateral is 180^(@) ?.

Prove that the figure formed by joining the points of the adjacent sides of a quadrilateral parallelogram.

Name the quadrilaterals whose diagonals. are perpendicular bisectors of each other

Prove that the figure formed by joining the mid-points of the pairs of consecutive sides of a quadrilateral is a parallelogram.

Prove that if the diagonals of a quadrilateral bisect each other at right angles, then the quadrilateral is a rhombus.

Sum of the angles of a quadrilateral is ................ .

Prove that the angle between internal bisector of one base angle and the external bisector of the other is equal to one-half of the vertical angles.