How to predict where a rectangle will go before being rotated (Processing)

I hope I'm asking this concisely enough. I'm wanting to run a script that will predict where a rectangle will end up when doing a rotation, before the rotation actually starts. So, if you're given a rectangle which is located on coordinates (40, 40) and you want the angle to change by 20 degrees, how would you predict or estimate the x y values of where that rectangle would end up? I'm wanting to do this estimation first, then store it in an array, and then compare it when the real rotation happens. For the prediction, I'd have thought it would be something like this...

  void setup(){

  size(825, 825);
  background(255);
  smooth();

  PShape Shape = createShape(GROUP);

  PShape rectangle = createShape(RECT, 40, 40, 120, 230); // with 40 and 40 being the x and y
  
  // extra point just to show where the x and y of the rectangle are //
  
  strokeWeight(5);
  stroke(0, 255, 0);
  PShape point = createShape(POINT, 40, 40);
 
  Shape.addChild(rectangle);
  Shape.addChild(point);

  int rectangleX = 40;
  int rectangleY = 40;

  int translationModifierX = 200;
  int translationModifierY = 200;

  // so this here would be the theoretical estimate on what the new x and y coordinates would be for the translation, before moving onto the rotation. This one's easy to predict, of course. //

  int newX = rectangleX + translationModifierX; 
  int newY = rectangleY + translationModifierY;

  // And here is where I'd be trying to estimate what the new x and y coordinates would be after rotated. //

  float rotatedX = newX*cos(20) - newY*sin(20);
  float rotatedY = newX*sin(20) + newY*cos(20);

  println("Final X Coordinate Prediction:", rotatedX);
  println("Final Y Coordinate Prediction:", rotatedY);

  pushMatrix();
  Shape.translate(newX, newY);
  Shape.rotate(radians(20));
  popMatrix();

  shape(Shape);

}

This printed prediction, though, is not that close to where the x y actually ends up. It actually ends up around 263, 292, but the print puts the x value as ~-121, and its y value at ~317. What I'm really needing to do is get this prediction's x and y coordinates to be the same as it would be when I run rectangle.rotate(radians(20)). I just want to be able to see where this rectangle would go before it actually goes there. I feel like it's a math problem. I'm obviously new, so I'd appreciate any assistance.

You need to use the relative (rectangleX/rectangleY), not the absolute (newX/newY) coordinates.

float rotatedX = newX + rectangleX*cos(radians(20)) - rectangleY*sin(radians(20));
float rotatedY = newY + rectangleX*sin(radians(20)) + rectangleY*cos(radians(20));