title: How to do dot/cross multiplication of Vectors with Sympy
body: <p>I would like to know how to do </p>
  
  <ul>
  <li>dot multiplication</li>
  <li>cross multiplication</li>
  <li>add/sub</li>
  </ul>
  
  <p>of vectors with the sympy library.  I have tried looking into the official documentation but I have had no luck or It was too complicated. Can anyone help me out on this?</p>
  
  <p>I was trying to do this simple operation</p>
  
  <pre><code>a · b = |a| × |b| × cos(θ)
  </code></pre>