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Pearson Geometry Common Core, 2011

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Pearson Geometry Common Core, 2011 View details

4. Compositions of Isometries

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Exercise 45 Page 576

A 90^(∘) rotation counterclockwise about the origin will change the coordinates of the vertices such that (a,b)→ (- b,a).

Practice makes perfect

Let's start by graphing the given coordinates of the triangle.

When a figure is rotated 90^(∘) counterclockwise about the origin, the coordinates of the image's vertices 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 image's vertices.

(a,b)	(- b,a)
A(0,4)	A'(- 4,0)
B(0,0)	B'(0,0)
C(- 3,- 1)	C'(1,- 3)

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

Subchapter links

Lesson Check p.573

Practice and Problem-Solving Exercises p.574-576

Standardized Test Prep p.576

Mixed Review p.576