1. Warm-Up
Name the angle relationships.
1.
2.
3.
4.
5.
<2 and <6
<4 and <6
<5 and < 8
<1 and <8
<3 and <6

2. Essential Question
What is a reflection? Draw an example of a
reflection.

3. Reflections
Unit 1, Day 4

4. Common Core GPS
MCC8.G.1: Verify experimentally the properties of
rotations, reflections, and translations:
a. Lines are taken to lines, and line segments to line
segments of the same length.
b. Angles are taken to angles of the same measure.
c. Parallel lines are taken to parallel lines.
MCC8. G. 2: Understand that a two-dimensional figure is
congruent to another if the second can be obtained
from the first by a sequence of rotations, reflections,
and translations; given two congruent figures, describe
a sequence that exhibits the congruence between
them.

5. Language of the Standards
Reflection: a transformation that “flips” a figure
over a line of reflection.
Reflection Line: a line that is the perpendicular
bisector of the segment with endpoints at a
pre-image point and the image of that after a
reflection.

6. Reflections
Reflections must take place over a line. We will
often see a reflection over the x-axis or the yaxis. For example,
Which line is the figure
reflected over?

7. Name the reflection line.

8. Name the reflection line.

9. Compare the Coordinates.
Now, let’s examine the coordinates and their
change once reflected.

10. Compare the Coordinates.
Now, let’s examine the coordinates and their
change once reflected.

11. Let’s Reflect…
Reflect the figure over the x – axis.

12. Let’s Reflect…
Reflect the figure over the y – axis.
How is the
reflection over
the y-axis
different from
the x-axis?

13. Reflect…
A volunteer to reflect over the x-axis.

14. Reflect…
A volunteer to reflect over the y-axis.

15. Congruent or Similar?
Are triangles J and S
congruent or similar
and how do you
know?

16. Work Session:
What is the reflection line?
1.
2.

18. 5. What is the line of reflection?
6. Name the vertices (coordinates) of triangle
ABC and triangle A’B’C’.
7. Is triangle ABC and triangle A’B’C’ congruent
or similar? How do you know?

19. Differentiation: Using the coordinate plane,
create your own polygon and reflect over a
reflection line. Remember to use the
apostrophes to indicate which figure is the
reflected figure. When directed by the
teacher, you will trade your polygon with
another student. You will list the reflected
coordinates for the figure as well as the
reflection line.

20. Closing
Discuss the task and any related questions to
check for understanding.