title: tan ( pi/2 ) in objective-c (math.h) not undefined
body: <p>I wrote this test code:</p>
  
  <pre><code>NSLog(@"%g", tan(M_PI / 2.0));
  </code></pre>
  
  <p>and the output of the console is:</p>
  
  <pre><code>1.63312e+16
  </code></pre>
  
  <p>The issues is about approximation, right? Did I make some mistakes or the <strong>tan</strong> function of <strong>math.h</strong> really doesn't handle this case itself (returning me INFINITY) ? shall I handle theese input cases myself (example: when I get pi/2 input value I return an error message) or is there a better (more elegant) way to get the correct value ?</p>
  
  <p>Thanks</p>