title: Efficient way to get the angle between two vectors in a single plane?
body: <p>If I know for a fact that the x and z values of the vectors will be identical,
  therefore im only concerned in measuring the 'vertical' angle of from the differences in the y plane, is there a more efficient method to do this compared to computing the dot product?</p>
  
  <p>My current code using the dot product method is as follows:</p>
  
  <pre><code>float a_mag = a.magnitude(); 
  float b_mag = b.magnitude();
  float ab_dot = a.dot(b);
  float c = ab_dot / (a_mag * b_mag);
  
  // clamp d to from going beyond +/- 1 as acos(+1/-1) results in infinity
  if (c &gt; 1.0f) {
      c = 1.0;
  } else if (c &lt; -1.0) {
      c = -1.0;
  }
  
  return acos(c);
  </code></pre>
  
  <p>I would love to be able to get rid of these square roots</p>