Unit 1 – Day 2 Reflections

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

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

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

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.

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

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

Example Write the rule and graph the image

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

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