2x2 matrix determinant
<a href="//commons.wikimedia.org/w/index.php?title=User:Hikin1987&amp;action=edit&amp;redlink=1" class="new" title="User:Hikin1987 (page does not exist)">Hikin1987</a>
2008
<span class="int-own-work" lang="en">Own work</span>