code: public final void mulInverse(Quaternion q1) {  
  		Quaternion  tempQuat = q1.clone();
  
  		tempQuat.inverse();
  		this.mul(tempQuat);
  	}
docs: Multiplies this quaternion by the inverse of quaternion q1 and places
  the value into this quaternion.  The value of the argument quaternion
  is preserved (this = this * q^-1).
  @param q1 the other quaternion