Definition:Quadrilateral/Dart
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Definition
A dart is an irregular quadrilateral with a reflex angle.
Deltoid
A deltoid is a dart such that:
- the $2$ sides which are adjacent to the reflex angle are equal to each other
- the other $2$ sides are also equal to each other.
Also defined as
Some sources prefer to reserve the term dart for what we define on $\mathsf{Pr} \infty \mathsf{fWiki}$ as a deltoid, that is, a reflex-angled trapezoid which has both pairs of adjacent sides equal, for example $EFGH$ in the diagram above.
Other uses restrict the term specifically to the Penrose dart in the Penrose tiles.