With each iteration, you're swapping the two coordinates, and then change sign of the first one:
First transformation
- Start with (3,1)
- Swap coordinates: (1,3)
- Change sign of the first coordinate: (-1,3)
Second transformation
- Start with (-1,3)
- Swap coordinates: (3,-1)
- Change sign of the first coordinate: (-3,-1)
Third transformation
- Start with (-3,-1)
- Swap coordinates: (-1,-3)
- Change sign of the first coordinate: (1,-3)
