Big Ideas Math Integrated I, 2016
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Big Ideas Math Integrated I, 2016 View details
3. Rotations
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Exercise 14 Page 566

If a point (a,b) is reflected in the line y=x, then its image is the point (b,a).

Practice makes perfect

Let's begin by drawing the segment XY and the line of reflection y=x.

If a point (a,b) is reflected in the line y=x, then its image is the point (b,a).

Point (a,b) (b,a)
X (- 3,1) (1,- 3)
Y (4,- 5) (- 5,4)

When we know the endpoints of X'Y' we can graph this image.

Next we have to do a rotation of 180^(∘) about the origin. When a figure is rotated 180^(∘) counterclockwise about the origin, the coordinates of the image's endpoints will change in the following way. (a,b)→ (- a,- b) Using this rule on the endpoints of XY, we can find the endpoints of X'Y',

Point (a,b) (- a,- b)
X' (1,- 3) (- 1,3)
Y' (- 5,4) (5,- 4)

Now we can graph X''Y''.

Finally, we will remove all unnecessary parts of the graph.