Final answer:
The coordinates of A' after a 90° counterclockwise rotation about the origin will be (-y, x), where (x, y) are the original coordinates of A.
Step-by-step explanation:
To determine the coordinates of A' after rotating point A 90° counterclockwise about the origin, you apply a specific transformation rule for 90° rotations in the coordinate plane. This rule is (-y, x), which means that if the original coordinates of point A are (x, y), then after rotating them 90° counterclockwise about the origin, the new coordinates A' will be (-y, x).
For example, if point A has coordinates (3, 4), applying the transformation gives us A' as (-4, 3). This is because you swap the x and y values and then change the sign of the new x value (originally y) to get the coordinate of A' in its new position.