Image shows that 3 points on unit circle can be isolated by elliptical (and circular) discs.
<a href="//commons.wikimedia.org/w/index.php?title=User:Peryeat&amp;action=edit&amp;redlink=1" class="new" title="User:Peryeat (page does not exist)">Peryeat</a>
<span class="int-own-work" lang="en">Own work</span>