 # A transformation is a change in the position, size, or

## Presentation on theme: "A transformation is a change in the position, size, or"— Presentation transcript:

A transformation is a change in the position, size, or
shape of a figure or graph. It is sometimes called a mapping. Examples of transformations are: translations, reflections, rotations, and dilations.

Preimage: the original figure Image: the figure after the transformation

Which of the transformations are examples of
Isometry: a transformation that does not change the size or shape of a figure Which of the transformations are examples of isometry? Translations, reflections, and rotations

Reflections 12-1 I CAN - Accurately reflect a figure in space.
- Reflect a figure across the x-axis, the y-axis the line y = x, or the line y = –x Holt Geometry

Reflection: Reflection is a transformation that moves a figure by flipping it across a line

Reflection The original figure is called the preimage and the reflected figure is called the image. A reflection is the reflected image always congruent to the preimage? What do we call this?

Example 1: Identifying Reflections
Tell whether each transformation appears to be a reflection. Explain. A. B. No; the image does not Appear to be flipped. Yes; the image appears to be flipped across a line.

Check It Out! Example 1 Tell whether each transformation appears to be a reflection. a. b. No; the figure does not appear to be flipped. Yes; the image appears to be flipped across a line.

We are going to reflect images on the coordinate plane across given lines 

Reflecting across vertical lines (x = a)
Reflect across x = -2 Step 1 – Draw line of reflection A B B' A' Step 2 – Pick a starting point, count over-ALWAYS vertically or horizontally to line D C D' C' Step 3 – Go that same distance on the other side of line Step 4 – LABEL THE NEW POINTS Step 5 – Continue with other points Do # 3 on your worksheet Label the coordinates of the preimage.

Reflecting across y-axis
Reflect the following shape across the y-axis Pre-image Image A'( , ) A( , ) A B( , ) B'( , ) B C( , ) C'( , ) C Do # 4 on your worksheet Label the coordinates of the preimage.

Reflecting across x-axis
Reflect the following shape across the x-axis Pre-image Image A'( , ) A A( , ) B( , ) B'( , ) B C C( , ) C'( , ) Do #5 on your worksheet Label the coordinates of the preimage.

F'( , ) I'( , ) S'( , ) H'( , ) Reflecting across the line y = x
Remember: Move ONLY vertically or horizontally…think about why? Pre-Image Image F( , ) F'( , ) I( , ) I'( , ) F I S( , ) S'( , ) H( , ) H'( , ) H S Do #6 on your worksheet Label the coordinates of the preimage.

Look back at the problems you just completed.
Compare the x and y-coordinates for the pre-image and image. Can you see a rule for each reflection?

Reflect the rectangle with vertices S(3, 4),
Check It Out! Reflect the rectangle with vertices S(3, 4), T(3, 1), U(–2, 1) and V(–2, 4) across the x-axis. The reflection of (x, y) is (x,–y). S(3, 4) S’(3, –4) V S U T T(3, 1) T’(3, –1) U(–2, 1) U’(–2, –1) V’ S’ U’ T’ V(–2, 4) V’(–2, –4) Graph the image and preimage.

Reflect across y = –x C’( , ) A’( , ) K’( , ) E’( , )