Answer:
(x, y) ⇒ (-y, x)
Step-by-step explanation:
You can see that the points (1, 2) and (3, 5) get mapped to (-2, 1) and (-5, 3), respectively. That is, the old value y, when negated, is the new value of x; and the old value of x is the new value of y.
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I find it easier to think of a 270° CW rotation as being the same as a 90° CCW rotation.
