Editing Concave polygon (section)

{{Short description|Simple polygon which is not convex}}
[[File:Simple polygon.svg|thumb|200px|An example of a concave polygon.]]
A [[simple polygon]] that is not [[convex polygon|convex]] is called '''concave''',<ref>{{citation |first=Jeffrey J. |last=McConnell |year=2006 |title=Computer Graphics: Theory Into Practice |isbn=0-7637-2250-2 |page=[https://archive.org/details/computergraphics0000mcco/page/130 130] |url=https://archive.org/details/computergraphics0000mcco/page/130 }}.</ref> '''non-convex'''<ref>{{Citation |last=Leff |first=Lawrence |title=Let's Review: Geometry |year=2008 |publisher=Barron's Educational Series |location=Hauppauge, NY |isbn=978-0-7641-4069-3 |pages=66}}</ref> or '''reentrant'''.<ref>{{citation |first=J.I. |last=Mason |year=1946 |title=On the angles of a polygon |journal=The Mathematical Gazette |volume=30 |issue=291 |jstor=3611229 |pages=237–238 <!--|do=10.2307/3611229--> |publisher=The Mathematical Association|doi=10.2307/3611229 }}.</ref> A concave polygon will always have at least one [[reflex angle|reflex interior angle]]—that is, an angle with a measure that is between 180° degrees and 360° degrees exclusive.<ref name=MOR>{{Cite web | url = http://www.mathopenref.com/polygonconcave.html | title = Definition and properties of concave polygons with interactive animation.}}</ref>