title: Calculate Euclidean distance between 4-dimensional vectors
body: <p>Let's say I have two 4-dimensional vectors (i.e. a and b) as follows:</p>
  
  <pre><code>a = {a1, a2, a3, a4}
  b= {b1, b2, b3, b4}
  </code></pre>
  
  <p>How do I compute the Euclidean distance between these vectors?</p>