<Tr> <Th> Area </Th> <Td> b × h (base × height); ab sin θ (product of adjacent sides and sine of any vertex angle) </Td> </Tr> <Tr> <Th> Properties </Th> <Td> convex </Td> </Tr> <P> In Euclidean geometry, a parallelogram is a simple (non-self - intersecting) quadrilateral with two pairs of parallel sides . The opposite or facing sides of a parallelogram are of equal length and the opposite angles of a parallelogram are of equal measure . The congruence of opposite sides and opposite angles is a direct consequence of the Euclidean parallel postulate and neither condition can be proven without appealing to the Euclidean parallel postulate or one of its equivalent formulations . </P> <P> By comparison, a quadrilateral with just one pair of parallel sides is a trapezoid in American English or a trapezium in British English . </P>

Parallelogram is a quadrilateral in which opposite sides are parallel