A parallelogram is a four-sided plane figure that has two sets of opposite parallel sides.
Every parallelogram is a polygon, and more specifically a quadrilateral.
Special cases of a parallelogram are the rhombus, in which all four sides are of equal length, the rectangle, in which the two sets of opposing, parallel sides are perpendicular to each other, and the square, in which all four sides are of equal length and the two sets of opposing, parallel sides are perpendicular to each other.
In any parallelogram, the diagonals bisect each other, i.e, they cut each other in half.
Prism (geometry) In geometry, an n-sided prism is a polyhedron made of an n-sided polygonal base, a translated copy, and n faces joining corresponding sides. Thus ... >
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Triangle A triangle is one of the basic shapes of geometry: a polygon with three vertices and three sides which are straight line segments. Any three ... >
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Tessellation A tessellation or tiling of the plane is a collection of plane figures that fill the plane with no overlaps and no gaps. One may also speak of ... >
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Euclidean geometry Euclidean geometry is a mathematical well-known system attributed to the Greek mathematician Euclid of Alexandria. Euclid's text Elements was the ... >
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Hyperbolic geometry In mathematics, hyperbolic geometry is a non-Euclidean geometry, meaning that the parallel postulate of Euclidean geometry is rejected. The parallel ... >
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Angle An angle is the figure formed by two rays sharing a common endpoint, called the vertex of the angle. Angles provide a means of expressing the ... >
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Tetrahedron A tetrahedron (plural: tetrahedra) is a polyhedron composed of four triangular faces, three of which meet at each vertex. A regular tetrahedron is ... >
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Antiprism An n-sided antiprism is a polyhedron composed of two parallel copies of some particular n-sided polygon, connected by an alternating band of ... >
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