Big Ideas Math: Modeling Real Life, Grade 8
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Big Ideas Math: Modeling Real Life, Grade 8 View details
3. Rotations
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Exercise 16 Page 61

When a point with coordinates (x,y) is rotated 270^(∘) clockwise about the origin, the coordinates of its image are (- y,x).

P'(- 4, -3), Q'(-4,- 1), R'(-1,- 2), S'(-1,- 4)

Practice makes perfect

A rotation is a transformation about a fixed point called center of rotation. Each point of the original figure and its image are the same distance from the center of rotation. When a clockwise rotation is performed about the origin, the coordinates of the image can be written in relation to the coordinates of the preimage.

Rotations About the Origin
90^(∘) Rotation 180^(∘) Rotation 270^(∘) Rotation

ccc Preimage & & Image [0.5em] (x,y) & → & (y,- x)

ccc Preimage & & Image [0.5em] (x,y) & → & (- x,- y)

ccc Preimage & & Image [0.5em] (x,y) & → & (- y,x)

We want to rotate a quadrilateral 270^(∘) clockwise about the origin. Therefore, we can use the information in the above table to find the coordinates of the image of each vertex. ccc Preimage & & Image (x,y) & → & (- y, x) [0.5em] P(-3,4) & & P'(- 4,- 3) [0.5em] Q(- 1,4) & & Q'(- 4,- 1) [0.5em] R(- 2,1) & & R'(- 1,- 2) [0.5em] S(- 4,1) & & S'(- 1,- 4) We can now plot the obtained points and draw the image of the given quadrilateral after the rotation!
preimage and image

Extra

Visualizing the Rotation
Let's rotate PQRS 270^(∘) clockwise about the origin so that we can see how it is mapped onto P'Q'R'S'.
rotate