title: cosine negative power in R
body: <p>I am trying to find the inverse cosine for a value in R.     </p>
  
  <pre><code>&gt; cos^-1(x)  
  </code></pre>
  
  <p>But </p>
  
  <pre><code>Error: attempt to apply non-function 
  </code></pre>
  
  <p>appears. Any suggestion?  </p>