code: @Override
      public Quaternionf invert() {
          final float lengthSquared = lengthSquared();
          if (Math.abs(lengthSquared) < GenericMath.FLT_EPSILON) {
              throw new ArithmeticException("Cannot invert a quaternion of length zero");
          }
          return conjugate().div(lengthSquared);
      }
docs: Inverts the quaternion. <br> Inversion of a quaternion <code>a</code> returns quaternion <code>a<sup>-1</sup> = a' / |a|<sup>2</sup></code> where <code>a'</code> is {@link #conjugate()
  conjugation} of <code>a</code>, and <code>|a|<sup>2</sup></code> is squared length of <code>a</code>. <br> For any quaternions <code>a, b, c</code>, such that <code>a * b = c</code> equations
  <code>a<sup>-1</sup> * c = b</code> and <code>c * b<sup>-1</sup> = a</code> are true.
  
  @return the inverted quaternion