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Big Ideas Math Geometry, 2014

BI

Big Ideas Math Geometry, 2014 View details

3. Rotations

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Exercise 7 Page 194

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 looking at the given polygon.

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.

△ ABC	(a,b)	(- b,a)
A	(- 3,2)	(-2,-3)
B	(2,4)	(- 4,2)
C	(3,1)	(- 1,3)

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

Subchapter links

Communicate Your Answer p.189

Monitoring Progress p.191-193