1. A ( , ) W ( , ) H ( , ) L ( , ) 0 2 A’ ( , ) W’ ( , ) H’ ( , )
Learning Objective
What are we going to do?
CFU
January 21, 2014 Review for QUIZ.
We will reflect1 geometric figures on a coordinate plane.
1 create a mirror image of (synonym)
2 making changes to original
Vocabulary
Standard 7.G.1 Verify experimentally the properties of Transformations2. Our focus today will be REFLECTIONS.
Activate Prior Knowledge
We have worked with a few different types of Transformations.
DILATION OF 2 A’ W’
ORIGINAL FIGURE NEW FIGURE
A ( , )
W ( , )
H ( , )
L ( , )
0 2
A’ ( , )
W’ ( , )
H’ ( , )
L’ ( , )
0 4 L’
2 2
4 4
0 -1
0 -2
-1 1
-2 2 H’
greater
Because the dilation is _______ than 1, our new image will be ________ than the original, in this case _______ the size of the original.
larger
twice
How do DILATIONS change the original figure?
What operations are used in dilations?
CFU 2

2. Translation: Move 1 unit to left, 6 units down
Concept Development
Ordered Pair
(2, 3)
x and y
Translating Ordered Pairs on the Coordinate Plane
X moves left (if negative) or right (if positive)
Y moves down (if negative) or up (if positive)
Translation: Move 1 unit to left, 6 units down
(-1, -6)
How do you translate a geometric figure?
In your own words, why must you also label points with letters?
CFU D’ J’ Z’

3. Concept Development
Ordered Pair
(2, 3)
x and y
Translating Ordered Pairs on the Coordinate Plane
X moves left (if negative) or right (if positive)
Y moves down (if negative) or up (if positive)
How do you translate a geometric figure?
In your own words, how do you determine which direction to move on x axis? On y axis?
CFU
Based on the translation stated above, which figure is the original (pre-image)? Which is the new image?

4. Reflections on the Coordinate Plane
Concept Development (Continued)
The line of reflection is often either the x-axis or the y-axis.
Preimage points (ordered pairs) can be measured from the line of reflection. The new image should be the same distance away.
When looking at the line of reflection, the corresponding points should be ___________.
CFU
Reflections on the Coordinate Plane

5. Guided Practice
Reflections1 take an image and create a mirror-like image across a line of reflection.
A preimage is the original shape or figure. Image refers to the new figure or shape that you will create.
A Reflection should be equal in distance from the line of reflection.
How can you use a grid (graph paper) to create a reflection?
CFU
1 mirror image of original (synonym)
Vocabulary
pre image image
______________________________________________________________________________________________________________________________________________

6. Plot your new points and label accordingly. Sketch your new figure.
Skill Development
Determine where the line of reflection is. The line of reflection will be horizontal (if line is the x-axis) and it will be vertical (if line is the y-axis). If the figure is on both sides of the line of reflection, there will be overlap with the new image.
Plot your new points and label accordingly. Sketch your new figure.

7. Directions: REFLECT EACH FIGURE ACROSS THE Y-AXIS.
Guided Practice
Determine where the line of reflection is. The line of reflection will be horizontal (if line is the x-axis) and it will be vertical (if line is the y-axis)
Plot your new points and label accordingly. Sketch your new figure.
Directions: REFLECT EACH FIGURE ACROSS THE Y-AXIS.

8. Directions: REFLECT EACH FIGURE ACROSS THE X-AXIS.
Guided Practice
Determine where the line of reflection is. The line of reflection will be horizontal (if line is the x-axis) and it will be vertical (if line is the y-axis)
Plot your new points and label accordingly. Sketch your new figure.
Directions: REFLECT EACH FIGURE ACROSS THE X-AXIS.

9. Skill Closure
Determine where the line of reflection is. Is the picture below showing reflection across the x-axis or the y-axis?
How can we determine if we have properly reflected the figure preimage (black figure)?
ON THE GRID BELOW, FIRST SKETCH THE REFLECTION OVER THE X-AXIS. THEN REFLECT THE ORIGINAL IMAGE OVER THE Y-AXIS. WHICH QUADRANT WILL NOT BE USED?
A reflection over a line is a transformation in which each point of the original figure (pre-image) has an image that is the same distance from the line of reflection as the original point but is on the opposite side of the line. 
Remember that a reflection is a flip.  In a reflection, the figure does not change size. 
How is a reflection similar to a translation?
How is a reflection different from a dilation?
CFU