The digon is the degenerate polygon (corresponding to a line segment) with Schläfli
symbol 
.
Digon
See also
Biangle, Dihedron, Hosohedron, Full Angle, Line Segment, Polygon, Trigonometry Angles--pi/2Explore with Wolfram|Alpha
Cite this as:
Weisstein, Eric W. "Digon." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Digon.html