Unit 1. day 6 diff slides

Warm-Up
Determine the scale factor of the similar
polygons.
1.
2.

Essential Question
How is a translation different from a reflection?

Reflections Day 2
Unit 1, Day 6

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.

Language of the Standards
What is a reflection?
What is a reflection line?

RE F L E CT I ONS R
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RE F L E CT I ONS R
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When an object is reflected in a mirror line, its image appears as though
it had been viewed through a mirror. All corresponding points on the object
and image are equidistant from and perpendicular to, the mirror line.
Object
Mirror
Line
Image

RE F L E CT I ONS R
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RE F L E CT I ONS R
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When an object is drawn on a grid you can reflect it in the mirror
line with the help of the squares. Here rectangle ABCD (object) is
reflected to A’B’C’D’ (image).
A B
C
D C’
A’
B’
D’

RE F L E CT I ONS R
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RE F L E CT I ONS R
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x
y
0 2 4 6 8
-2
-4
-6
-8
2
4
-2
-4
Triangle T is to be reflected in the y axis,
Kite K is to be reflected in the x axis and
Pentagon P is to be reflected in the y axis.
T
K
A
B
C
D
A
B
C
D
T’
A’
B’
C’
K’
A’
B’
D’
C’
P
A
B
C
D
E
P’
A’
B’
C’
D’
E’
Reflecting objects
in an X,Y grid.

Lines of Reflection
Not all reflection lines include the x and y-axis.
We may also reflect an object using a line that
is shifted on the axis such as y = 3 and x = -2.
Will this shift in the line of reflection change the
shape or size of the object? How do you
know?

RE F L E CT I ONS R
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RE F L E CT I ONS R
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x
y
0 2 4 6 8
-2
-4
-6
-8
2
4
-2
-4
Trapezium T, is to be reflected in the lines x = 1
and y = 2.
A B
C
T
D
Reflecting objects
in an X,Y grid.
x = 1
y = 2
A’
B’
C’ D’
T’
A’’ B’’
C’’
D’’
T’’
Previous work on
“Straight Line
Graphs (Drawing) ”
from the Algebra
area is assumed.

Reflect
Let’s try a reflection at y = -1.

Reflect
Let’s reflect the same object at x = -2.

What is the line of reflection?
Name the line of reflection.

Q5
RE F L E CT I ONS R
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RE F L E CT I ONS R
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x
y
0 2 4 6 8
-2
-4
-6
-8
2
4
-2
-4
T
K
C
T’
Reflecting objects
in an X,Y grid.
T’’
Question 5.
Describe the transformation that takes Triangle T to:
(a) T’ (b)T’’
Reflection in
the line x = -1
Reflection in
the line y = 1

Work Session:
Name the line of reflection.

Graph the figure of the image after the given
transformation.

Antonio and his friend, Brittany, were at a summer math
camp that had a large coordinate plane drawn on the
gym floor. Antonio challenged Brittany to try and
mirror him as he traveled around the first quadrant.
Map Antonio’s and Brittany’s movements on this
coordinate plane.
Antonio began at (2, 1) and walked to (3, 5); Brittany
decided to begin at (-2, 1), then tried to mirror Antonio
by walking to (-3, 5). Antonio jumped to (5, 5) and
side-stepped to (4, 3); Brittany jumped to (-5, 5) and
side-stepped to (-4, 3). Antonio returned to (2, 1) and
Brittany returned to (-2, 1).

7. Did Brittany mirror Antonio? _________________
8. If Brittany had instead begun at (-2, 1), walked to (-4,
3), side-stepped to (-5, 5), jumped to (-3, 5) and then
returned to (-2, 1), could she claim that she created a
mirror image of Antonio’s path? Justify your answer.

Closing:
What have you learned about reflections?

Unit 1. day 6 diff slides

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Unit 1. day 6 diff slides