title: Laplace transform of non-explicit function
body: <p>I am working with a function <code>p(t)</code> that is function of the time variable <code>t</code>. I don't have the explicit expression of <code>p</code> as function of time and I would like to apply Laplace transform to an expression that includes the function <code>p</code>. 
  I started by defining all the parameters as symbolic in MATLAB</p>
  
  <pre><code>syms m ms k t p f;
  f=(m+ms/3)*(diff(p(t),t))^2+k*(p(t))^2;
  </code></pre>
  
  <p>When I execute those lines, I get this error.</p>
  
  <p><a href="https://i.stack.imgur.com/qTLkD.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/qTLkD.png" alt="enter image description here"></a></p>
  
  <p>I think the problem comes from the fact that I'm trying to differentiate the function <code>p</code> with respect to <code>t</code> but I'm not sure. 
  Is there a way to get the Laplace transform of the function <code>f</code>?</p>