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Pearson Geometry Common Core, 2011

PG

Pearson Geometry Common Core, 2011 View details

Chapter Test

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Exercise 3 Page 607

The image of a point (a,b) that is rotated 90^(∘) counterclockwise about the origin is (- b,a).

A'(0,3) B'(2,1) C'(5,3) D'(1,7)

Practice makes perfect

Let's start by looking at the given polygon.

When a figure is rotated 90^(∘) counterclockwise about the origin, the coordinates of the vertices of the image will change in the following way.

(a,b)→ (- b,a) Using this rule and the vertices of the polygon, we can find the x- and y-coordinates of the vertices of the image.

(a,b)	(- b,a)
A(3,0)	A'(0,3)
B(1,-2)	B'(2,1)
C(3,-5)	C'(5,3)
D(7,-1)	D'(1,7)

Knowing the vertices of A'B'C'D', we can draw the image.

As we can see, A'(0,3), B'(2,1), C'(5,3), and D'(1,7) are the coordinates of the image of ABCD.