title: How to solve an error in using simplify() method in R?
body: <p>It's the first time I try to calculate an expression's derivative using R. I have tried the following code:</p>
  <pre><code>library(Ryacas)                       # open the Ryacas package.
  f &lt;- expression(asin(2*x/(1 + x^2)))  # insert the expression.
  d &lt;- D(f, 'x')                        # find the expression's derivative.
  print(d)                              # print the derivative of f.
  simple_d &lt;- simplify(d)               # make the mathematical expression of the derivative simpler.
  print(simple_d)                       # print the simply expressed derivative of f.
  </code></pre>
  <p>And I received the following error message about the usage of the <code>simplify()</code> method.</p>
  <pre><code>Error in UseMethod(&quot;simplify&quot;) : 
    no applicable method for 'simplify' applied to an object of class &quot;call&quot;
  </code></pre>
  <p>Any ideas on this ? How should I properly use <code>simplify()</code> method on an expression like <code>d</code> ?</p>
  <p>Thank you!</p>