What name is given to a quadrilateral with two pairs of parallel sides but not at right angles?
Orthodiagonal quadrilateral Orthodiagonal quadrilateral In Euclidean geometry, an orthodiagonal quadrilateral is a quadrilateral in which the diagonals cross at right angles. In other words, it is a four-sided figure in which the line segments between non-adjacent vertices are orthogonal (perpendicular) to each other. A kite is an orthodiagonal quadrilateral in which one diagonal is a line of symmetry. The kites are exactly the orthodiagonal quadrilaterals that contain a circle tangent to all four of their sides; that is, the kites are the tangential orthodiagonal quadrilaterals. A rhombus is an orthodiagonal quadrilateral with two pairs of parallel sides (that is, an orthodiagonal quadrilateral
Quadrilateral terms of the sides and two opposite angles: where the sides in sequence are "a", "b", "c", "d", where "s" is the semiperimeter, and "A" and "C" are two (in fact, any two) opposite angles. This reduces to Brahmagupta's formula for the area of a cyclic quadrilateral when . Another area formula in terms of the sides and angles, with angle "C" being between sides "b" and "c", and "A" being between sides "a" and "d", is In the case of a cyclic quadrilateral, the latter formula becomes formula_7 In a parallelogram, where both pairs of opposite sides and angles