Graphing & Describing “Reflections”

We have learned that there are 4 types of transformations: 1)Translations 2)Reflections 3)Rotations 4)Dilations The first 3 transformations preserve the size and shape of the figure. In other words… If your pre-image (the before) is a trapezoid, your image (the after) is a congruent trapezoid. If your pre-image contains parallel lines, your image contains congruent parallel lines. If your pre-image is an angle, your image is an angle with the same measure.

Yesterday… our lesson was ALL about translations. Today… our lesson will focus on reflections.

Section 1:Comparing a translation to a reflection. Section 2:Performing a reflection over the x- or y-axis. Section 3:Performing a reflection over a line. Section 4: Describing a reflection. Let’s Get Started

Which of the below is the translation and which is the reflection. Be ready to explain how you know to the class. #1 #2 Turn and Discuss

Which of the below is the translation and which is the reflection. Be ready to explain how you know to the class. #1 #2 Turn and Discuss

You can use a slide arrow to show the direction and distance of the movement. A translation is a slide that moves a figure to a different position (left, right, up or down) without changing its size or shape and without flipping or turning it. If You Remember…

A reflection (flip) creates a mirror image of a figure.

Section 1:Comparing a translation to a reflection. Section 2:Performing a reflection over the x- or y-axis. Section 3:Performing a reflection over a line. Section 4: Describing a reflection. Moving On

A reflection is a flip because the figure is “flipped” over a line. Each point in the image is the same distance from the line as the original point. Check to see if the pre-image and image are congruent. A Reflection is a Flip over a Line A B C A' B' C' t

Reflect the figure across the y-axis. Check to see if the pre-image and image are congruent. Step 1: Start with any vertex and count the number of units to the specified axis (or line). Step 2: Measure the same distance on the other side of the axis (or line) and place a dot. Label using prime notation. Step 3: Repeat for the other vertices. STEPS and EXAMPLE

Let’s name the coordinates of each figure. A (, )A' (, ) B (, )B' (, ) C (, )C' (, ) D (, )D' (, ) Pre-image Image reflection across y-axis Reflection Across the Y-AXIS Compare the coordinates of the pre-image to the image. What do you notice?

Let’s take a look at the same pre-image and see what it looks like after being reflected across the x-axis …

Here is the same pre-image but this time it is reflected across the x-axis. Pre-image Image reflection across x-axis Reflection Across the X-AXIS Compare the coordinates of the pre-image to the image. What do you notice?

Name the coordinates of your reflection: You Try #1

Reflect figure QRST across the x-axis Name the coordinates of your reflection: You Try #2

Turn and Discuss

Section 1:Comparing a translation to a reflection. Section 2:Performing a reflection over the x or y-axis. Section 3:Performing a reflection over a line. Section 4: Describing a reflection. Moving On

Reflections Across a Vertical or Horizontal Line You may be asked to reflect a figure across a line that is not the x-axis or the y-axis. Let’s see how to do that…

First, draw the line of reflection. Then follow the normal steps for reflecting over a line. Example over a Vertical Line line of reflection

First, draw the line of reflection. Then follow the normal steps for reflecting over a line. Example over a Horizontal Line line of reflection

Name the coordinates of your reflection: You Try #3

Name the coordinates of your reflection: You Try #4

Section 1:Comparing a translation to a reflection. Section 2:Performing a reflection over the x or y-axis. Section 3:Performing a reflection over a line. Section 4: Describing a reflection. Moving On

Describing a Reflection In this Section, you will be given a reflection that has already been performed, and you will describe what occurred. Example:

You Try Describe the below reflections. 5)6)

Figure 1 A B C D You Try 7)Which of the following represents a single reflection of Figure 1?

You Try 8)Describe the reflection below. A)across the y-axis B)across the x-axis C)across the line y=-3 D)across the line x=4

You Try

Questions

END OF POWERPOINT