An infinitesimal rectangular loop used to proove Green's theorem.
<a href="//commons.wikimedia.org/w/index.php?title=User:Math_buff&amp;action=edit&amp;redlink=1" class="new" title="User:Math buff (page does not exist)">Math buff</a>, Shawn Eastwood
<span class="int-own-work" lang="en">Own work</span>