Quadrilaterale

Sex genera quadrilateralium.

Taxinomia quadrilateralium per diagramma Hasseanum descripta.

Quadrilaterale (e quadri- praefixo < 'quattuor' + latus) in geometria Euclidea est polygonum laterum quattuor, quibus sunt quattuor margines (latera) et quattuor vertices (anguli). Quod etiam appellatur tetragonum (Graece tetra 'quattuor' + gon 'angulus'), aliorum polygonorum simile, exempli gratia pentagonorum. Res, quia gon 'angulum' significat, per similitudinem appellatur quadrangulum, saepe 4-angulum scriptum. Quadrilaterale cui sunt vertices $A$, $B$, $C$, et $D$ aliquando denotatur $◻ABCD$.

Quadrilateralia sunt aut simplicia (non intersecantia), aut multiplicia (intersecantia vel transversa). Quadrilateralia simplicia sunt aut convexa aut concava.

• Rectangulum
• Trapezium

Nexus externi

• "Quadrilaterals Formed by Perpendicular Bisectors," "Projective Collinearity," et "Interactive Classification" quadrilateralium apud Cut-the-knot.
• Definitions and examples of quadrilaterals et "Definition and properties of tetragons" apud Mathopenref.
• "A (dynamic) Hierarchical Quadrilateral Tree" apud Dynamic Geometry Sketches.
• "An extended classification of quadrilaterals" (PDF). Formula:Webarchive at "Dynamic Math Learning Homepage." Formula:Webarchive
• Villiers, Michael de. "The role and function of a hierarchical classification of quadrilaterals." (PDF).