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Warm Up

Warm Up Given that ∆ ABC  ∆ DEF, identify a segment or angle congruent to each of the following. 1. 2. 3. 4. 5. 6. Objective. Name and draw reflections. Try this:. Fold a sheet of paper in half. Without opening the paper draw a quadrilateral that is not regular and label it ABCD.

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Warm Up

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  1. Warm Up Given that ∆ABC  ∆DEF, identify a segment or angle congruent to each of the following. 1. 2. 3. 4. 5. 6.

  2. Objective Name and draw reflections.

  3. Try this: • Fold a sheet of paper in half. Without opening the paper draw a quadrilateral that is not regular and label it ABCD. • Turn the folded paper over and trace the image of ABCD onto the opposite side of the paper. Label the vertex corresponding to A as A’. (continue with B, C, and D.) • Open the paper and draw line l along the fold between the two quadrilaterals. Line l is the line of reflection.

  4. Try this continued: • How do you think the measures of each side compare with its reflection? The angles? • Draw a line from A to A’, B to B’, C to C’ and D to D’. • Use a protractor to measure the angle that AA’ and l intersect. • If you measure from A to line l, how does that distance compare to the distance from A’ to line l? How about for the other points?

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

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

  7. Example 2: Drawing Reflections Copy the triangle and the line of reflection. Draw the reflection of the triangle across the line. Step 1 Through each vertex draw a line perpendicular to the line of reflection.

  8. Example 2 Continued Step 2 Measure the distance from each vertex to the line of reflection. Locate the image of each vertex on the opposite side of the line of reflection and the same distance from it.

  9. Example 2 Continued Step 3 Connect the images of the vertices.

  10. Check It Out! Example 2 Copy the quadrilateral and the line of reflection. Draw the reflection of the quadrilateral across the line.

  11. Practice Problems 1. Tell whether the transformation appears to be a reflection. yes 2. Copy the figure and the line of reflection. Draw the reflection of the figure across the line.

  12. Other words to know • Orientation – order of the vertices when named (can be either clockwise or counterclockwise) • Image – the picture after the reflection (preimage is the original picture) • Line of symmetry – a line that can be drawn through a picture so that it cuts the picture exactly in half (use the fold test)

  13. S’ S V T’ R U T S T’ U’ T R’ S’ V’ Which is the image? Notice the orientation.

  14. Homework: Section 4-2 #1-31

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