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If the diagonals of a quadrilateral bisect each other, it is a ________.

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A diagonal of a quadrilateral is a line segment that joins two _______ vertices of the quadrilateral.

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The number of sides in a regular polygon having measure of an exterior angle as 72° is _______.

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The adjacent sides of a parallelogram are 5cm and 9cm. It's perimeter is ________.

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A nonagon has _______ sides.