Square (geometry)
A square is a quadrilateral in which all sides have equal length and all angles are right angles.
![[asy] import markers; pair A, B, C, D; A = (-1, 1); B = (1, 1); C = (1, -1); D = (-1, -1); draw(A--B--C--D--cycle); draw(rightanglemark(A, B, C)); draw(rightanglemark(B, C, D)); draw(rightanglemark(C, D, A)); draw(rightanglemark(D, A, B)); draw(A--B--C--D--cycle, StickIntervalMarker(4)); [/asy]](http://latex.artofproblemsolving.com/b/0/9/b099e8fd521b2fcda4322d23b57eb040ea4a5bf4.png)
Equivalently, all squares are the regular quadrilaterals.
Introductory
Area
The area of a square can be found by squaring the square's side length: the area 
of a square with side length 
is 
.
Perimeter
The perimeter 
of a square can be found by multiplying the square's side length by four - 
.
Diagonal
The length of either diagonal of a square can be obtained by the Pythagorean theorem. 
See Also
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