Big Ideas Math: Modeling Real Life, Grade 8
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Big Ideas Math: Modeling Real Life, Grade 8 View details
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Exercise 20 Page 93

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

A'(- 2,- 4), B'(- 2,- 2), C'(- 4,- 3)

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 triangle 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] A(- 4,2) & & A'(- 2,- 4) [0.5em] B(- 2,2) & & B'(- 2,- 2) [0.5em] C(- 3,4) & & C'(- 4, - 3) We can now plot the obtained points and draw the image of the given triangle after the rotation!
preimage and image

Extra

Visualizing the Rotation
Let's rotate △ ABC 270^(∘) clockwise about the origin so that we can see how it is mapped onto △ A'B'C'.
rotate