Cauchy Schwarz Inequality
<a href="//commons.wikimedia.org/wiki/User:DnetSvg" title="User:DnetSvg">dnet</a>
self-made, based on <a class="external free" href="https://en.wikipedia.org/wiki/Image:060819_cauchy_schwarz_inequality.png">http://en.wikipedia.org/wiki/Image:060819_cauchy_schwarz_inequality.png</a> (PD)