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Rotation

CONCEPTS

Rotation of a point (x, y)

• Rotate CW 90°: (x, y) –> (y, –x)

• Rotate CW 180°: (x, y) –> (–x, –y)

• Rotate CW 270°: (x, y) –> (–y, x)


EXAMPLE: Rotation can be done logically or with equations

• Rotate (3, 6) 90° CW

• Rotate (3, 6) 180° CW

• Rotate (3, 6) 270° CW


PRACTICE PROBLEMS

Question 1 Point A is rotated 450° about the origin. If it starts at (2.5, 2.5), what is the point after it’s rotated?






-- Answer -- (-2.5, 2.5)








After rotation,

the new point is D or (-2.5, 2.5)

ACT PRACTICE PROBLEMS

71c

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