<script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=default"></script>
$$\vec{a} \cdot \vec{b}=0$$
<script type="text/javascript" src="http://cdn.mathjax.org/mathjax/latest/MathJax.js?config=default"></script>
$$\vec{a} \cdot \vec{b}=0$$