Name_____________________________
A.
Modified KHM Problem 5.1 Coordinate Rules for Reflections
1. Plot and label the following coordinates and connect the points to create a triangle.
A (-1, 1), B (-7, 2), and C (-5, 8)
Please label the
figures on your
own copy. I ran
out of time for
the small details.
2. Reflect the triangle across the y-axis. Label the image of each point. What are the new coordinates?
A’ ( -1 , -1 ), B’ (-7 , -2 ) and C’ (-5 , -8 )
3. Describe the pattern that relates each point (x, y) to its image. Which points remain unchanged?
The x-coordinate stays the same and the y-coordinate changes to its opposite value.
4. Reflect the triangle across the x-axis. Label the image of each point. What are the new coordinates?
A” (1 , -1 ), B” (7 , -2 ) and C” (5 , -8 )
5. Describe the pattern that relates each point (x, y) to its image. Which points remain unchanged?
The x-coordinate changes to the opposite value and the y-coordinate stays the same.
Edited 4/1/13
Adapted from CMP2: Kaleidoscopes, 5.1
Name_____________________________
Modified KHM Problem 5.1 Coordinate Rules for Reflections
B. List the coordinates of the Quadrilateral ABCD.
A ( 6 ,8 )
B(8 ,6 )
C(8 ,4)
D(4 ,2)
C. Reflect Quadrilateral ABCD across the y-axis and label the image coordinates A’, B’, C’ and D’.
1. List the coordinates of the image of Quadrilateral ABCD under a reflection across the y-axis.
A’ ( -6 , 8 )
B’ ( -8 , 6 )
C’ ( -8 , 4 )
D’ ( -4 , 2 )
2. Compare the coordinates of each original point with the coordinates of its image. Use the
patterns you see to complete this coordinate rule for finding the image of any point (x,y) under a
reflection across the y-axis:
(x,y)
( -x , y )
D. Reflect Quadrilateral A’B’C’D’ across the x-axis and label the image coordinates A”, B”, C” and D”.
1. List the coordinates of the image of Quadrilateral A’B’C’D’ under a reflection across the x-axis.
A” ( -6 , -8)
B” ( -8 , -6 )
C” ( -8 , -4)
D” ( -4 , -2 )
2. Compare the coordinates of each original point with the coordinates of its image. Complete this
coordinate rule for finding the image of any point (x,y) under a reflection across the x-axis:
(x,y)
( x , -y)
Edited 4/1/13
Adapted from CMP2: Kaleidoscopes, 5.1
Name_____________________________
Modified KHM Problem 5.1 Coordinate Rules for Reflections
E. Apply the above coordinate rule for reflecting across the x-axis to the quadrilateral below.
1. Is the coordinate rule for reflecting across the x-axis still
true when the figure crosses more than one quadrant?
How do you know?
Each of the y-coordinates changed to their
opposite while the x-coordinate remained the
same value.
Edited 4/1/13
Adapted from CMP2: Kaleidoscopes, 5.1