To determine the correct function mapping for a 90-degree counterclockwise rotation about the origin, we examine each option:
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Option #1: (x,y)→(y,−x): This mapping represents a rotation of 90 degrees clockwise.
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Option #2: (x,y)→(−y,x): This mapping represents a rotation of 90 degrees counterclockwise.
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Option #3: (x,y)→(−x,−y): This mapping reflects the point across the origin (180-degree rotation).
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Option #4: (x,y)→(y,x): This mapping reflects the point across the line y = x (which is not a rotation).
Therefore, the correct option for a 90-degree counterclockwise rotation about the origin is:
Option #2: (x,y)→(−y,x).