Do Now Section 9 3 Perform Reflections Vocabulary

Do Now §

Section 9. 3 Perform Reflections

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

Identify Reflections

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)

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.

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)

Examples

Practice §

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?

Line symmetry § Determine the number of lines of symmetry for the figure