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Published byCleopatra Garrett Modified over 9 years ago
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12.1 – Reflections 12.5 – Symmetry M217 – Geometry
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ISOMETRY A movement or “translation” of a figure that preserves its original dimensions. Reflections Translations Rotations
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C C Reflection – A transformation that uses a line that acts like a mirror. Reflection Line of Reflection
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Reflection Properties: Over y-axis (x, y) → ( ) A (-2, 4) B (2, -1) C (0, 4) D (-3, 0)
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Reflection Properties: Over x-axis (x, y) → ( ) A (-2, 4) B (2, -1) C (0, 4) D (-3, 0)
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Reflection Properties: Over y=x (x, y) → ( ) A (3, 4) B (1, 1) C (-3, 2) D (-32, 11) y = x
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Ex: Reflection in the line y=1 y = 1 A (-1, 3) B (3, -2) C (0, 1) D (-2, 0)
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Ex: Reflection in the line x = -2 x = -2 Triangle ABC: A (-1, 3)B (-3, -2)C (-4, 1)
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The Line of Symmetry is the imaginary line where you could fold an image and have both halves match exactly.
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Determine the number of lines of symmetry in each logo 1. 2. 3. 4. 5.
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None – Go Hawks!!! Back
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One – Go Bulls!!! Back
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Almost one… Go Bears!!! Back
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How many does the Mercedes logo have?
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How many does the Star of David have?
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Rotational Symmetry : if a figure can be mapped onto itself by a rotation of 180 o or less
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rotational symmetry : if a figure can be mapped onto itself by a rotation of 180 o or less
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rotational symmetry : if a figure can be mapped onto itself by a rotation of 180 o or less
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rotational symmetry : if a figure can be mapped onto itself by a rotation of 180 o or less
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Do You Get It? Is this a reflection? How many lines of symmetry? Does it have rotational symmetry? A A’ B B’ C C’
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Do You Get It? If point R (-4,-5) is reflected over the y-axis, what are the coordinates of R’? If point S (0, 2) is reflected over the line x = -5, what are the coordinates of S’? Given points T ( -4, 3) and T’ ( -4, -2), what is the line of reflection?
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