Name: _________________________________________________________________ Date: _______________________
Day 14LAB: Reflections CC Geometry (M1L14)
Opening Exercise Use your compass and straightedge to construct the perpendicular bisector of each of the segments connecting 𝐴 to 𝐴′ , 𝐵 to 𝐵′ , and 𝐶 to 𝐶′ . a) What do you notice about these perpendicular bisectors?
EXAMPLE #1: Construct the segment that represents the line of reflection for quadrilateral 𝐴𝐵𝐶𝐷 and its image
𝐴′𝐵′𝐶′𝐷′ .
Steps to finding the line of reflection:
1. Measure C to C’ (or any matching points)
2. Construct the perpendicular bisector of
CC’. This is the line of reflection.
2.
What is true about each point on 𝐴𝐵𝐶𝐷 and its corresponding point on 𝐴′𝐵′𝐶′𝐷′ ?
EXAMPLES #2 & 3: Construct the line of reflection across which each image below was reflected.
3.

We write a reflection of image P over line l as r ( P )
r = P = L =
1
. Write the transformation that is identified: r l
(A)
2. Write the transformation that is identified: r m
(ABC)
3. Write in notation form: A reflection of Triangle ABC over line t.
4. Write in notation form: A reflection of AB over line c.
PRACTICE
1.
Construct the line of reflection for the following figure:
To construct a line of reflection we are constructing a ______________________ _____________________________.
SUMMARY
 A reflection carries segments onto segments of _____________ length.
 A reflection carries angles onto angles of ___________________ measure.
 A reflection is an example of a ______________________________________________ because reflections preserve both
___________________and _________________________________ the same.

Example 1
Reflect the given image across the line of reflection provided:
1) Point on A, make arc that will hit the line of reflection twice. (Label the intersections D and E)
2) Measure your compass D to A(sharp end on D) and make a circle
3) Measure your compass E to A(sharp end on E) and make a circle
4)The intersection point of these 2 circles opposite the line of reflection label as A’
Example 2
Reflect the given image over the line of reflection
A
B m
L

Example 3
Reflect the given image over the line of reflection
A
B C
Practice
1.
Reflect the given image over the line of reflection m l
SUMMARY
1.
What is the relationship (lengths of segments and angle measures) between the pre-image and the image that you constructed?
2.
What is the name of a transformation that preserves angles measure and length of sides?

Name: ________________________________________________________ Date: __________________
Day 14: Rotations/Intro Reflections HW RIGID MOTION
1.What are the 3 rigid motions discussed in class?__________________, ___________________,
________________
2.Rigid motions preserve ____________ of segments and ____________ measure.
3. Locate the center of rotation from the figure from its original (solid line) to its image (dashed line). (Use steps from CW)
A B
A'
B'
NOTATION FOR ROTATIONS
4. Precisely define the rigid motion transformation identified
𝑅
𝐶,30°
(𝑃) __________________________________________________________________________________
5. The following diagram is quadrilateral ABCD rotated 244˚ CCW or
116˚ CW around point C, write this in notation form.
NOTATION FOR REFLECTIONS
6. Precisely define the rigid motion transformation identified 𝑟 𝑙
(𝐴𝐵) ___________________________________________________________________________________
7. The following diagram is a reflection, write this in notation form

8. Construct the line of reflection. (Use steps from CW)
9. Reflect triangle ABC over line m. (Use steps from CW)