title: Trigonometry in PHP (Inverse Sine)
body: <p>I didn't pay as much attention as I should have in math class, don't shoot me.</p>
  
  <p>Anyway... I'm trying to calculate a degree of rotation. I have my hypotenuse &amp; opposite lengths (it is a right triangle).</p>
  
  <p>So I'm guessing the equation should look like:</p>
  
  <pre><code>$radians = sin-1 ($opposite/$hypotenuse);
  </code></pre>
  
  <p>I see a sine function (<code>sin</code>) but I don't see an inverse sine function (i.e. sin-1).</p>
  
  <p>Do I just <code>pow(sin($opposite/$hypotenuse),-1)</code> it, or so I have my trig all confused?</p>