1. Do Now

2. Section 9.3 Perform Reflections

3. Vocabulary
Reflection: transformation that uses a line like a mirror to reflect an image
(flip an image over a line)
Line of reflection: the line that acts as a mirror

4. Identify Reflections

5. Reflection in the x axis
Triangle DEF is the image of triangle ABC after a reflection in the x axis.
Point A is 2 spaces away from the x axis, so
Point D is 2 spaces away from the axis.
A(-7, 2) B(-3, 2) C(-3, 4)
D(-7, -2) E(-3, -2) F(-3, -4)
Rule for reflection in the x axis: (x, y) → (x, -y)

6. Reflection in the x axis
Graph triangle ABC with vertices A(4, 2) B(5, 6) C(7, 3)
Graph the image of triangle ABC after a reflection in the x
axis and list the coordinates of the image.

7. Reflection in the y axis
Graph segment GE with vertices G(-3, 4) E(2, -1)
Graph the image of segment GE after a reflection in the y
axis and list the coordinates of the image.
Rule for reflection in the y axis:
(x, y) → (-x, y)

8. Examples

11. Practice

12. Line Symmetry
Line of symmetry = line that divides a figure into two equal parts
Example: How many
lines can you draw
through the heart to
get equal parts?

13. Line symmetry
Determine the number of lines of symmetry for the figure