Lesson 4
1. Lesson 4
1.12. Explore 8
Module 5: Geometry
A rotation can be used to change the orientation of a figure. Rotations can be in a clockwise or a counterclockwise direction.
The coordinates of points can be predicted for some angles using a strategy similar to that used earlier. The mappings for a 90° and a 180° clockwise rotation are shown. Notice that the mapping for 180° is the same as performing a 90° rotation twice.
|
90° Clockwise Rotation |
180° Clockwise Rotation |
Description |
The x- and y-coordinates trade places, and the x-coordinate (now y) changes sign. |
Both the x- and y-coordinates change sign. |
Example |
(5, 3) → (3, −5) |
(5, 3) → (−5, −3) |
Self-Check 4
- Answer “Discuss the Ideas” questions 3.a, 3.b, and 3.c from page 223 of the textbook. Answer
- Answer “Build Your Skills” questions 2 and 6 from pages 227 and 228 of the textbook. Answer
Share 3
With a partner or in a group, discuss the following question.
Thus far, you have learned many rules for different transformations. Describe a strategy that will help you decide how a set of coordinates will change after a transformation, without having to memorize these rules.
If required, place a summary of your discussion in your course folder.
Add the following terms to your copy of Glossary Terms:
- transformation
- translation
- reflection
- dilation
- rotation
- scale factor