Symmetry and Reflection

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Symmetry and Reflection

• Mathematics
• Grades 6-8

Teacher Information
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Teacher Information

• Content This lesson provides an introduction to
  the concepts of symmetry and rotation.
• Grade Level 7
• Creator Abby Neiburger
• Curriculum Objective/MAP Standard IIIB.
  Identifies lines of symmetry in natural and
  geometric figures. MA-2, MA-4, MA-5, 1.6, 2.4,
  3.6, 4.2, 4.3
• Students will need paper and pencil for
  note-taking purposes. They will also need paper
  and pencil for completing the alphabet activity
  at the end of the presentation.

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What is symmetry?

• In plain terms, a figure that is symmetric is the
  same on both sides.
• If you can imagine drawing a line through a
  figure and having it look like it is reflected
  through a mirror, then the image is symmetrical.
• The imaginary line is called a line of symmetry.
• Here are some examples of symmetric figures.

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Lines of Symmetry

• If you draw a horizontal line through the center
  of the B, you will notice that the top is
  reflected over to the bottom. This is a
  horizontal line of symmetry.
• If you draw a vertical line through the center of
  the T, you will notice that the right side is
  reflected over to the left side. This is a
  vertical line of symmetry.

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Lines of Symmetry Continued

• Objects can have more than one line of symmetry.
  The letter X has diagonal lines of symmetry.
  What other lines of symmetry does this letter
  have?
• The letter O is a very unique letter. Can you
  make a distinction between O and other letters?
  How would you group the different letters of the
  alphabet?

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Rotation

• Turning figures around a point

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Rotating figures around a point

• The given point for this alien is the center of
  its stomach. To rotate this alien, we turn it
  around the center of its body. In each picture,
  the alien has been rotated 90 clockwise. The
  concept of rotation can be used with any figure
  or shape.

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Your Turn

• Do the figures at the right display a rotation?
• If so, how many degrees do you think the figure
  rotated?
• How else could this figure be rotated?

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Describe this!

• What would the figure at the left look like if it
  was rotated 90 counter-clockwise?
• What would it look like if it was rotated 180
  counter-clockwise?
• What kind of symmetry does this figure have?

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Activity

• Move through the alphabet considering only
  capital, block letters. For each letter, record
  the following information by creating a table
• Describe the line(s) of symmetry
• Illustrate what the letter will look like rotated
  90, 180, and 270
• The following slide begins the table for you.

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The Alphabet

• Copy this table and continue for the rest of the
  alphabet.
• When finished with your table, right a paragraph
  about a job or career where this information
  about symmetry and rotation might be useful.

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Words to Remember

• Transformations are movements of figures.
• Symmetric figures can be folded over a line of
  symmetry and appear as a mirror image.
• Rotations turn a figure around a certain point.