A two-dimensional <a href="https://en.wikipedia.org/wiki/Isosceles_set" class="extiw" title="en:Isosceles set">isosceles set</a>, points for which all triples form isosceles triangles, consisting of the vertices and center of a regular pentagon. The shaded regions show 4 of the 20 isosceles triangles formed by these points.
<a href="//commons.wikimedia.org/wiki/User:David_Eppstein" class="mw-redirect" title="User:David Eppstein">David Eppstein</a>
<span class="int-own-work" lang="en">Own work</span>