1. Unit 1 – Day 2
Reflections

2. Warm Up
Suppose a translation slides the point X(-3, 4) to the point X’(-1, 1). Write a rule (x, y)  ( ___ , ___ ) that describes this translation.
The points A(2, 7) and B(-5, 4) are translated by the vector <-4, 1> Determine the coordinates of the image points A’ and B’
10 minutes
Have Homework and Homework Stamp Sheet out.
Place Info Sheet in Turn in Folder in basket
End

3. Reflection
Definition: A Reflection is a transformation in which the preimage is flipped across a line of symmetry.

4. Line of Symmetry
The Line of Symmetry is the line that the preimage is reflected over.
When you connect the preimage and image with a line segment, the Line of Symmetry will be the Perpendicular Bisector of the segment

5. Group Work
Just like with translations, line reflections can be expressed using coordinates. In this investigation, you will build coordinate models for reflections across vertical and horizontal lines, as well as across the lines y = x and y = -x.
Time Keeper: 15 minutes
Resource Manager: Problem 8 and 9 Worksheet (1/member)
Reader: Read problems out loud to group
Spy Monitor: Check in with other groups if you are stuck
Page 202 in book
When finished, Resource Manager should grab 10 and 11 Worksheet.

6. Questions 10 and 11 Time Keeper: Set 20 minutes
Resource Manager: Grab worksheet for each member
Reader: Read problems out loud to group
Spy Keeper: Check with other groups if you are stuck
Page 203

7. General Rules for Line Reflections
Reflection across
The x-axis:
The y-axis:
The line y = x:
The line y = -x

8. Example
Write the rule and graph the image

9. Reflection over other lines
Remember! You can reflect across ANY line by thinking about the perpendicular bisector!

10. Assessment
Class Discussion: What are some real-world examples of reflections? How do they relate to what we learned today?
Homework: Worksheet