Rectangle
A closed planar Quadrilateral with opposite sides of equal lengths 
and 
, and with four Right Angles. The Area of the rectangle is
and its Diagonals are of length
A Square is a degenerate rectangle with
.See also Golden Rectangle, Perfect Rectangle, Square
References
Beyer, W. H. (Ed.) CRC Standard Mathematical Tables, 28th ed. Boca Raton, FL: CRC Press, p. 122, 1987. Eppstein, D. ``Rectilinear Geometry.''http://www.ics.uci.edu/~eppstein/junkyard/rect.html.
- Unitary Divisor
- Unitary Group
- Unitary Matrix
- Unitary Multiperfect Number
- Unitary Multiplicative Character
- Unitary Perfect Number
- Unitary Sociable Numbers
- Unitary Transformation
- Unitary Unimodular Group
- Unit Circle
- Unit Disk
- Unit Fraction
- Unit Matrix
- Unit Point
- Unit Ring
- Unit Sphere
- Unit Square
- Unit Step
- Unit Vector
- Unity
- Univalent Function
- Univariate Function
- Univariate Polynomial
- Universal Graph
- Universal Statement