A regular hendecagon is one possible answer. A regular hendecagon is one possible answer. A regular hendecagon is one possible answer. A regular hendecagon is one possible answer.

regular hendecagon has internal angles of 147.27 degrees. The area of a regular hendecagon with side length a is given by A regular hendecagon is not constructible with compass and straightedge; this animation shows an approximation:

A right hendecagon can have no parallel sides because there are eleven sides to a hendecagon. It is not a requirement that there be any pairs of parallel sides in an irregular hendecagon, although there could be one or more pairs.