Rectangle

In geometry, a rectangle is defined as a quadrilateral polygon in which all four angles are right angles.

Related Topics:
Geometry - Quadrilateral - Polygon - Right angle

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From this definition, it follows that a rectangle has two pairs of opposite sides of equal length; that is, a rectangle is a parallelogram. A square is a special kind of rectangle where all four sides have equal length; that is, a square is both a rectangle and a rhombus. A rectangle that is not a square is colloquially known as an oblong.

Related Topics:
Length - Parallelogram - Square - Rhombus

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Of the two opposite pairs of sides in a rectangle, the length of the longer side is called the length of the rectangle, and the length of the shorter side is called the width. The area of a rectangle is the product of its length and its width; in symbols, A = lw. For example, the area of a rectangle with a length of 5 and a width of 4 would be 20, because 5 × 4 = 20. See the picture above right.

Related Topics:
Area - Product

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In calculus, the Riemann integral can be thought of as a limit of sums of the areas of arbitrarily thin rectangles.

Related Topics:
Calculus - Riemann integral - Limit - Sum

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