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12.3: Geometric Translations

Difficulty Level: At Grade Created by: CK-12
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What if Lucy lived in San Francisco, S, and her parents lived in Paso Robles, P? She will be moving to Ukiah, U, in a few weeks. All measurements are in miles. Find:

a) The component form of PS,SU and PU.

b) Lucy’s parents are considering moving to Fresno, F. Find the component form of PF and UF.

c) Is Ukiah or Paso Robles closer to Fresno?

After completing this Concept, you'll be able to answer these questions.

Watch This

CK-12 Foundation: Chapter12TranslationsA

Learn more about translations by watching the video at this link.

Guidance

A transformation is an operation that moves, flips, or changes a figure to create a new figure. A rigid transformation is a transformation that preserves size and shape. The rigid transformations are: translations (discussed here), reflections, and rotations. The new figure created by a transformation is called the image. The original figure is called the preimage. Another word for a rigid transformation is an isometry. Rigid transformations are also called congruence transformations. If the preimage is A, then the image would be labeled A, said “a prime.” If there is an image of A, that would be labeled A′′, said “a double prime.”

A translation is a transformation that moves every point in a figure the same distance in the same direction. In the coordinate plane, we say that a translation moves a figure x units and y units. Another way to write a translation rule is to use vectors. A vector is a quantity that has direction and size.

In the graph below, the line from A to B, or the distance traveled, is the vector. This vector would be labeled AB because A is the initial point and B is the terminal point. The terminal point always has the arrow pointing towards it and has the half-arrow over it in the label.

The component form of AB combines the horizontal distance traveled and the vertical distance traveled. We write the component form of AB as 3,7 because AB travels 3 units to the right and 7 units up. Notice the brackets are pointed, 3,7, not curved.

Example A

Graph square S(1,2),Q(4,1),R(5,4) and E(2,5). Find the image after the translation (x,y)(x2,y+3). Then, graph and label the image.

The translation notation tells us that we are going to move the square to the left 2 and up 3.

(x,y)S(1,2)Q(4,1)R(5,4)E(2,5)(x2,y+3)S(1,5)Q(2,4)R(3,7)E(0,8)

Example B

Name the vector and write its component form.

The vector is DC. From the initial point D to terminal point C, you would move 6 units to the left and 4 units up. The component form of DC is 6,4.

Example C

Name the vector and write its component form.

The vector is EF. The component form of EF is 4,1.

Watch this video for help with the Examples above.

CK-12 Foundation: Chapter12TranslationsB

Concept Problem Revisited

a) PS=84,187,SU=39,108,PU=123,295

b) PF=62,91,UF=185,204

c) You can plug the vector components into the Pythagorean Theorem to find the distances. Paso Robles is closer to Fresno than Ukiah.

UF=1852+(204)2275.4 miles,PF=622+912110.1 miles

Vocabulary

A transformation is an operation that moves, flips, or otherwise changes a figure to create a new figure. A rigid transformation (also known as an isometry or congruence transformation) is a transformation that does not change the size or shape of a figure. The new figure created by a transformation is called the image. The original figure is called the preimage. A translation is a transformation that moves every point in a figure the same distance in the same direction. A vector is a quantity that has direction and size. The component form of a vector combines the horizontal distance traveled and the vertical distance traveled.

Guided Practice

1. Find the translation rule for TRI to TRI.

2. Draw the vector ST with component form 2,5.

3. Triangle ABC has coordinates A(3,1),B(7,5) and C(2,2). Translate ABC using the vector 4,5. Determine the coordinates of ABC.

4. Write the translation rule for the vector translation from #3.

Answers:

1. Look at the movement from T to T. T is (-3, 3) and T is (3, -1). The change in x is 6 units to the right and the change in y is 4 units down. Therefore, the translation rule is (x,y)(x+6,y4).

2. The graph is the vector ST. From the initial point S it moves down 5 units and to the right 2 units.

3. It would be helpful to graph ABC. To translate ABC, add each component of the vector to each point to find ABC.

A(3,1)+4,5B(7,5)+4,5C(2,2)+4,5=A(1,4)=B(3,0)=C(6,3)

4. To write 4,5 as a translation rule, it would be (x,y)(x4,y+5).

Practice

  1. What is the difference between a vector and a ray?

Use the translation (x,y)(x+5,y9) for questions 2-8.

  1. What is the image of A(6,3)?
  2. What is the image of B(4,8)?
  3. What is the preimage of C(5,3)?
  4. What is the image of A?
  5. What is the preimage of D(12,7)?
  6. What is the image of A′′?
  7. Plot A,A,A′′, and A′′′ from the questions above. What do you notice? Write a conjecture.

The vertices of ABC are A(6,7),B(3,10) and C(5,2). Find the vertices of ABC, given the translation rules below.

  1. (x,y)(x2,y7)
  2. (x,y)(x+11,y+4)
  3. (x,y)(x,y3)
  4. (x,y)(x5,y+8)

In questions 13-16, ABC is the image of ABC. Write the translation rule.

For questions 17-19, name each vector and find its component form.

  1. The coordinates of DEF are D(4,2),E(7,4) and F(5,3). Translate DEF using the vector 5,11 and find the coordinates of DEF.
  2. The coordinates of quadrilateral QUAD are Q(6,1),U(3,7),A(4,2) and D(1,8). Translate QUAD using the vector 3,7 and find the coordinates of QUAD.

Vocabulary

Center of Rotation

Center of Rotation

In a rotation, the center of rotation is the point that does not move. The rest of the plane rotates around this fixed point.
Image

Image

The image is the final appearance of a figure after a transformation operation.
Preimage

Preimage

The pre-image is the original appearance of a figure in a transformation operation.
Transformation

Transformation

A transformation moves a figure in some way on the coordinate plane.
Translation

Translation

A translation is a transformation that slides a figure on the coordinate plane without changing its shape, size, or orientation.

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Difficulty Level:

At Grade

Grades:

Date Created:

Jul 17, 2012

Last Modified:

Feb 26, 2015
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