Polygon
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In geometry, a polygon is a plane figure made up of line segments connected to form a closed polygonal chain.
The Giant's Causeway, in Northern Ireland
Triangle
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A triangle is a polygon with three corners and three sides, one of the basic shapes in geometry. The corners, also called vertices, are zero-dimensional points while the sides connecting them, also called edges, are one-dimensional line segments. The triangle's interior is a two-dimensional region. Sometimes an arbitrary edge is chosen to be the base, in which case the opposite vertex is called the apex.
