A rectangle is a quadrilateral in which all angles are right angles.

[asy] size(200); pair A, B, C, D; A = (-377,233); B = (377,233); C = (377,-233); D = (-377,-233); dot("$A$",A,1.5*dir(A),linewidth(4)); dot("$B$",B,1.5*dir(B),linewidth(4)); dot("$C$",C,1.5*dir(C),linewidth(4)); dot("$D$",D,1.5*dir(D),linewidth(4)); draw(A--B--C--D--cycle); [/asy]

Every rectangle is a parallelogram and so has all the properties of a parallelogram. In addition, rectangles have congruent diagonals.

Squares are the only rectangles which are also rhombuses.

All rectangles are cyclic quadrilaterals.

See Also


British Flag Theorem

Ptolemy's Theorem

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