1. Module 2 Lesson 2
Reflections
Reflections

2. Real-life reflections
Animation
Architecture
Graphic Design

3. Reflections
Reflection: a transformation in which a figure is flipped over a line of reflection. This line can be thought of as a mirror in which the image is a reflection of the pre-image. A reflection creates a mirror image of each point of a figure.
For this class, our line of reflection will be either the x-axis or the y-axis on a coordinate grid.

4. Reflection
Tell whether the red figure is a reflection of the blue figure.
This figure is a reflection.
This figure is not a reflection.

5. Example H
Reflect over the x-axis E Y

6. Reflecting over the y-axis
Coordinates of each vertex of a triangle and its image are shown.
Do you see a pattern in the change from the preimage to the image?
Preimage Image
Preimage
Image
(-3, -2) (3, -2)
(-10, 0) (10, 0)
(-2, 3) (2, 3)
When a point is reflected over the y-axis, its x-coordinate is multiplied by -1.

7. Reflecting over the x-axis
Coordinates of each vertex of a triangle and its image. Do you see a pattern in the change from the preimage to the image?
Preimage Image
(-2, 2) (-2, -2)
(-1, 7) (-1, -7)
(6, 5) (6, -5)
When a point is reflected over the x-axis, its y-coordinate is multiplied by -1.

8. Your turn!
Graph the triangle with vertices J(0, 1), K(1, 4), and L( 5, 2). Reflect the triangle over the y-axis and label it.

9. Your turn! Graph the quadrilateral with vertices S(-3,2),
T(-1, 4), U(-4, 5), and
V(-5, 3). Reflect the quadrilateral over the x-axis and label it.

10. Translation Game