Concave polygon

A simple polygon that is not convex is called concave,^[1] non-convex^[2] or reentrant.^[3] A concave polygon will always have at least one reflex interior angle—that is, an angle with a measure that is between 180 degrees and 360 degrees exclusive.^[4]

^ McConnell, Jeffrey J. (2006), Computer Graphics: Theory Into Practice, p. 130, ISBN 0-7637-2250-2.
^ Leff, Lawrence (2008), Let's Review: Geometry, Hauppauge, NY: Barron's Educational Series, p. 66, ISBN 978-0-7641-4069-3
^ Mason, J.I. (1946), "On the angles of a polygon", The Mathematical Gazette, 30 (291), The Mathematical Association: 237–238, doi:10.2307/3611229, JSTOR 3611229.
^ "Definition and properties of concave polygons with interactive animation".

[1] McConnell, Jeffrey J. (2006), Computer Graphics: Theory Into Practice, p. 130, ISBN 0-7637-2250-2.

[2] Leff, Lawrence (2008), Let's Review: Geometry, Hauppauge, NY: Barron's Educational Series, p. 66, ISBN 978-0-7641-4069-3

[3] Mason, J.I. (1946), "On the angles of a polygon", The Mathematical Gazette, 30 (291), The Mathematical Association: 237–238, doi:10.2307/3611229, JSTOR 3611229.

[MOR-4] "Definition and properties of concave polygons with interactive animation".

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