Reflections Lesson, TEKS 8.10C

​Do your Warm-Up!

What is our TEKS?

TEKS 8.10C:

The student will explain the effect of reflections over the x‐ or y‐axis as applied to two‐dimensional shapes on a coordinate plane using an algebraic representation.

Reflections, TEKS 8.10C (R)

It's time for our lesson . . .

​Reflections

You can take notes in your journal or lined paper, but be sure to pay attention to the IXL video.

Open Ended

What is one thing that you learned from the video?

Reflections:

• Represents the flipping of an image

• When an object is reflected, the pre-image and image are always congruent (SAME SIZE AND SAME SHAPE).

• Each point in the image and pre-image is the same distance from the line of reflection. (They are mirror images of each other.)

Multiple Choice

What is a reflection?

• When you turn an object around a point.

• When you slide an object form one place to another.

• When you flip or mirror an object across a line.

• When you resize an object.

Open Ended

Where do we see reflections in the real world?

Multiple Choice

When a figure is reflected over a line of reflection, the new image is congruent to the original. True or False

• True

• False

Multiple Choice

True or false: When a point is reflected across a line of symmetry, it remains the same distance from the line.

• true

• false

Line of Reflection:

• The line of reflection is the axis that the point or figure is being reflected across.

• It is also known as the line of symmetry.

Multiple Choice

Identify line of reflection.

• x axis

• y axis

• y = x

• y = -x

Multiple Choice

What axis is the triangle being reflected over?

• X-axis

• Y-axis

Reflections across the y-axis:

• (x, y) --> (-x, y)

• The y coordinate stays the same.

• The x coordinate changes sign.

• A(-8, 7) --> A'(8, 7)

Multiple Choice

Which answer shows a reflection across the y-axis?

• a

• b

• c

• d

Reflections over the x axis:

• (x, y) --> (x, -y)

• The x coordinate stays the same.

• The y coordinate changes sign.

• A(-8, 7) --> A'(-8, -7)

Multiple Choice

Which answer shows a reflection across the x-axis?

• d

• c

• b

• a

​Reflection Rules:

• ​Over the x-axis:  (x, -y) means keep the sign of x and change the sign of y.

 

• Over the y-axis: (-x, y) means keep the sign of y and change the sign of x.

Multiple Choice

What is the image of Z(-1, 4) after a reflection over the y axis?

• Z'(4, -1)

• Z'(-1,-4)

• Z'(4, 1)

• Z'(1, 4)

Multiple Choice

What is the image of S(2,-8), after a reflection over the line x axis?

• S'(-2,-8)

• S'(2, 8)

• S'(-8,2)

• S'(8,-2)

Pay attention as you work through the problems with the teacher.

Time for Guided Practice . . .

Reflections, TEKS 8.10C (R)

Multiple Choice

I DO:

How do you represent reflection over the x axis algebraically?

• (-y, -x)

• (x + a, y + b)

• (x , -y)

• (-x, y)

Multiple Choice

WE DO:

Find K' if the figure is reflected across the x-axis

• (4, 1)

• (-1, -4)

• (1, -4)

• (1, 4)

Multiple Select

YOU DO:

Select all the sets that are reflections across the X AXIS.

• A(5, 6) --> A'(5, -6)

• B(3, -8) --> B'(3, 8)

• C(5, -5) --> C'(-5, -5)

• D(-6, -1) --> D'(-6, 10

• E(1, 6) --> E'(1, -6)

​​Use your journal, lined paper, or dry erase board to practice solving the Quizizz problems on your own. Do as many problems as you can until the timer rings.

Time for Independent Practice . . .

Reflections, TEKS 8.10C (R)

Multiple Choice

Identify line of reflection.

• x axis

• y axis

• y = x

• y = -x

Multiple Choice

What is this transformation?

(x, y) ----> (-x, y)

• Reflect over the x axis

• Reflect over the y-axis

• Slide down 1

• slide left 1

Multiple Choice

Reflect Point C over the y-axis:

• (-3, 2)

• (3,2)

• (-2,3)

• (3,0)

Multiple Choice

Reflect Point C over the y-axis:

• (-3, 2)

• (3,2)

• (-2,3)

• (3,0)

Multiple Choice

Reflect over x-axis. Which point would be at (3, -6)

• A

• B

• C

• H

Multiple Choice

What is the Algebraic Notation for this Reflection?

• (x, y) → (y, x)

• (x, y) → (-x, y)

• (x, y) → (-y, -x)

• (x, y) → (x, -y)

Multiple Choice

Where will A' be at, if triangle ABC is reflected across the y-axis using the rule: (x, y) --> (-x, y)?

• (2, 1)

• (1, -2)

• (-1, 2)

• (-2, 1)

Multiple Choice

Triangle GHI is reflected across the x-axis.  What are the coordinates of I'?

• (-2, 6)

• (2, 6)

• (-6, -2)

• (6, 2)

Multiple Choice

∆BCD contains the points: B(2,3) C(2,1) D(5,1). If the triangle is reflected across the x-axis, what will B' be?

• B'(2, -3)

• B'(-2, 3)

• B'(-2, -3)

• B'(2, 3)

Multiple Choice

Point C (-5, 4)

Reflect over the x-axis.

What is C'?

• (5, 4)

• (-5, -4)

• (5, -4)

• (-5, 4)

Time for your Mastery Check:

It's time to assess your skills using a STAAR-related problem. Carefully select your answer to the next problem to test your knowledge. You will use this for your Self-Assessment.

Reflections, TEKS 8.10C (R)

Multiple Choice

What is the Algebraic Notation for this Reflection?

• (x, y) → (y, x)

• (x, y) → (-x, y)

• (x, y) → (-y, -x)

• (x, y) → (x, -y)

Poll

Self-Assessment:

• I'm an expert. I got this! (I can teach this skill to others.)

• I'm a Practitioner. I can do this with more practice. (I can re-do this lesson through Google Classroom.)

• I'm a Novice. I need help learning this skill! (I can come to tutoring to get the help I need, or I can ask an Expert for help.)