anchor.diff:  a|Formula
   
   a|angle in degrees +
  -a 
  +a
   a| to convert angle a from degrees to radians +
   new float angle phi
   a|phi = a / 180 * FastMath.PI; +
   OR +
  -phi=a.mult(FastMath.DEG_TO_RAD); 
  +phi=a.mult(FastMath.DEG_TO_RAD);
   
   a|angle in radians +
  -phi 
  +phi
   a| to convert angle phi from radians to degrees +
   new float angle a
  -a|a = phi * 180 / FastMath.PI 
  +a|a = phi * 180 / FastMath.PI
   
   a|radian angle and x axis +
  -phi, x 
  +phi, x
   a|to rotate around x axis +
   new quaternion q0
   a|q0.fromAngleAxis( phi, Vector3f.UNIT_X )
   
   a|radian angle and y axis +
  -phi, y 
  +phi, y
   a|to rotate around y axis +
   new quaternion q0
   a|q0.fromAngleAxis( phi, Vector3f.UNIT_Y )
   
   a|radian angle and z axis +
  -phi, z 
  +phi, z
   a|to rotate around z axis +
   new quaternion q0
   a|q0.fromAngleAxis( phi, Vector3f.UNIT_Z )
  
positive.code: 
  a|two points, a fraction +
  p1, p2, h=0.5f
  a|the point “halfway (h=0.5f) between the two points +
  new interpolated point p0
  a|p0 = FastMath.interpolateLinear(h,p1,p2)
  
  
negative.code: = Math Cheat Sheet
  :revnumber: 2.0
  :revdate: 2020/07/13
  
  
  == Formulas
  