title: Calculating derivative in a given point - matlab
body: <p>I would like to calculate the derivative of the following function in Matlab in point x=1.0:</p>
  
  <pre><code> v = sin(x)+ cos(3*x)
  </code></pre>
  
  <p>I tried this but it returns py = []</p>
  
  <pre><code>sym x,
  x=1.0,
  y=sin(x) + cos(3*x),
  py=diff(y);
  </code></pre>