If you use matrices: (Sorry, but I don't know how to make real matrix symbols here.)
counter-clockwise matrix: | cosθ -sinθ | clockwise matrix: | cosθ sinθ | | sinθ cosθ | | -sinθ cosθ |
1) Point (2,2) 90° clockwise: | cos 90° sin 90° | X | 2 | | -sin 90° cos 90° | | 2 |
2) Point (-1,4) 90° clockwise: | cos 90° sin 90° | X | -1 | | -sin 90° cos 90° | | 4 |
3) Point (3,2) 90° counter-clockwise: | cos 90° -sin 90° | X | 3 | | sin 90° cos 90° | | 2 |
4) Point (-1.4) 90° counter-clockwise: | cos 90° -sin 90° | X | -1 | | sin 90° cos 90° | | 4 |
If you have trouble with the matrices, please ask.