Transformations on a grid
The question
90° counterclockwise about O ()
(0, −3) 90° counterclockwise about O
How it works.
(0, −3)
0, −3swap−3, 0
(0, −3)→(3, 0)
- 01
Start where the point is: (0, −3). The move is 90° counterclockwise about O, and the question is only where those two numbers end up.
- 02
A quarter turn SWAPS the two numbers — going 0 across and −3 up becomes going −3 across and 0 up — and then one of them changes sign, because the turn carries the point into a different quarter of the grid.
- 03
Turning counterclockwise, that gives (3, 0).