What are we going to do?

CFU

Learning Objective

Activate Prior Knowledge

Standard 7.G.1 Verify experimentally the properties of Transformations2. Our focus today will be REFLECTIONS.

We will reflect1 geometric figures on a coordinate plane.

DILATION OF 0.5Y ( , )R ( , )T ( , )

Y’ ( , )R’ ( , )T’ ( , )

-2 3 2 1

-1 -2

-1 1.5 1 0.5

-0.5 -1

Y’

R’

T’

Because the dilation is less than 1, our new image will

be smaller than the original, in this case ½ the

size of the original.

We have worked with a few different types of Transformations.

1 create a mirror image (synonym) 2 making changes to original

Vocabulary

How do DILATIONS change the original figure?

What operations are used in dilations?

CFU 2

We first looked at Dilations. Dilations change the size through enlargement or reduction, but do not alter the shape. All sides maintain proportional relationships.

1 2 3 4 5 6 7 8 9 10

2

10

4

5

6

7

8

9

3

1

x-axis

y-axis

The coordinate plane is a flat surface made by the intersection of two perpendicular3 number lines. An ordered pair describes4 the location of a point on the coordinate plane using x- and y-coordinates.

How do you translate a geometric figure?

In your own words, what does it mean to translate an ordered pair?

“Translating an ordered pair means ______________.”

CFUTranslating5 Ordered Pairs on the Coordinate Plane

3 crossing at a 90 degree angle4 shows (synonym)5 moving in one or more directions (synonym)

Vocabulary

Activate Prior Knowledge

o Locate the point (4,4).

o In order to move from the (4,4) to Point T’s location,

how far does the point need to move horizontally? How far does it move vertically?

– the horizontal number line.

– the vertical number line.

The origin is where the x-axis and y-axis intersect.

(4, 4)44

T

Ordered Pair

(2, 3)

x and y

+4

+5

(+4 ) RIGHT

(+5 ) UP

How do you translate a geometric figure?

In your own words, how do you determine which direction to move on x axis? On y axis?

CFU

Translating Ordered Pairs on the Coordinate PlaneX moves left (if negative) or right (if positive)Y moves down (if negative) or up (if positive)

Concept Development

Ordered Pair

(2, 3)

x and y

(-6) = LEFT

(+2) = UP

How do you translate a geometric figure?

In your own words, why must you also label points with letters?

CFU

Translating Ordered Pairs on the Coordinate PlaneX moves left (if negative) or right (if positive)Y moves down (if negative) or up (if positive)

Concept Development

Ordered Pair

(2, 3)

x and y

Translation: Move 3 units to left, 4 units down

J’ Z’

D’

Concept DevelopmentReflections6 take an image and create a mirror-like image across a line of reflection.

A preimage is the original shape or figure. Image refers to the new figure or shape that you will create.

A Reflection should be equal in distance from the line of reflection.

How can you use a grid (graph paper) to create a reflection?

CFU

6 mirror image of original (synonym)

Vocabulary

The line of reflection is often either the x-axis or the y-axis.

Preimage points (ordered pairs) can be measured from the line of reflection. The new image should be the same distance away.

Reflections on the Coordinate Plane

Concept Development (Continued)

Look at Point A. Calculate the number of units Point A is from the Y axis. How can you use this to determine the position of the new point?

How does this work for Point B?

How does this work for point C?

CFU

Guided Practice

Reflections6 take an image and create a mirror-like image across a line of reflection.

A preimage is the original shape or figure. Image refers to the new figure or shape that you will create.

A Reflection should be equal in distance from the line of reflection.

How can you use a grid (graph paper) to create a reflection?

CFU

6 mirror image of original (synonym)

Vocabulary

Determine where the line of reflection is. The line of reflection will be horizontal (if line is the x-axis) and it will be vertical (if line is the y-axis)

Plot your new points and label accordingly. Sketch your new figure.

Skill Development / Guided Practice

Determine where the line of reflection is. The line of reflection will be horizontal (if line is the x-axis) and it will be vertical (if line is the y-axis)

Plot your new points and label accordingly. Sketch your new figure.

Guided Practice

Directions: REFLECT EACH FIGURE ACROSS THE Y-AXIS.

Determine where the line of reflection is. The line of reflection will be horizontal (if line is the x-axis) and it will be vertical (if line is the y-axis)

Plot your new points and label accordingly. Sketch your new figure.

Guided Practice

Directions: REFLECT EACH FIGURE ACROSS THE X-AXIS.

Determine where the line of reflection is. Is the picture below showing reflection across the x-axis or the y-axis?

How can we determine if we have properly reflected the figure preimage (black figure)?

Skill Closure

• A reflection over a line is a transformation in which each point of the original figure (pre-image) has an image that is the same distance from the line of reflection as the original point but is on the opposite side of the line.

• Remember that a reflection is a flip. In a reflection, the figure does not change size.

How is a reflection similar to a translation?

How is a reflection different from a dilation?

CFU