I've tried to rotate my rectangle, but it does not work properly.

Here is part of my code, I found it in another post:

```
#define DEGREES_TO_RADIANS(x) (M_PI * x / 180.0)
-(void)drawRect:(NSRect)rect
{
   CGContextRef cRef = [[NSGraphicsContext currentContext] graphicsPort];

   // points[] - this is a CGPoints array, length_one is a double value
   CGRect rect_one = CGRectMake(points[0].x, points[0].y, (CGFloat)length_one, 40);

   // I've print out the origin of old one and new one
   NSLog(@"old rect -- %f, %f", rect_one.origin.x, rect_one.origin.y);

  float centerX = rect_one.origin.x + (rect_one.size.width / 2.0);
  float centerY = rect_one.origin.y + (rect_one.size.height / 2.0);

  CGAffineTransform rotation = CGAffineTransformMakeRotation(DEGREES_TO_RADIANS(10));
  CGAffineTransform moveAnchor = CGAffineTransformMakeTranslation(centerX, centerY);

  CGAffineTransform centeredRotation = CGAffineTransformConcat(moveAnchor, rotation);

  CGRect rotatedRect = CGRectApplyAffineTransform(rect_one, centeredRotation);
  CGContextAddRect(cRef, rotatedRect);

  // new one
  NSLog(@"new rect -- %f, %f", rotatedRect.origin.x, rotatedRect.origin.y);
}

```

And the origin changed a lot even I can not find my new rectangle from the view. 
Old origin is (x = 263.3, y = 502.8) and the new origin is (x=506.1, y=1132.0) How does this system work especially how to assign the angle of rotation? If possible, could you guys help me brief explain it. Thanks a lot!!!!