<a href="https://en.wikipedia.org/wiki/Trapezoidal_rule" class="extiw" title="en:Trapezoidal rule">Trapezoidal rule</a> illustration
<a href="//commons.wikimedia.org/wiki/User:Oleg_Alexandrov" title="User:Oleg Alexandrov">Oleg Alexandrov</a>
<span class="int-own-work" lang="en">Own work</span>