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Rotational Symmetry 3-2A

Rotational Symmetry 3-2A. What is rotational symmetry? How do you identify a figure that has rotational symmetry?. How Many Degrees…. 180 ° 90° 270°. …are in a half turn? …are in a quarter turn? …three quarters turn?. Definition.

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Rotational Symmetry 3-2A

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  1. Rotational Symmetry 3-2A What is rotational symmetry? How do you identify a figure that has rotational symmetry?

  2. How Many Degrees… 180° 90° 270° …are in a half turn? …are in a quarter turn? …three quarters turn?

  3. Definition A rotation is a transformation that turns a set of points about one point, the center of rotation. The pre-image and image of any point are the same distance from the center of rotation. P (Pre-image) 45° Angle of rotation Q Center of rotation P’ (Image)

  4. P (Pre-image) 45° Angle of rotation Q Center of rotation P’ (Image) Definition continued The angle of rotation measures how much a point is turned about the center. For example, if point P is rotated 45° clockwise about center of rotation Q,

  5. Rotating Triangles Rotate triangle RST 90° about point C. R Z Label the images of points R,S, and T points X, Y, and Z . X C Draw CR. S T Use a protractor to draw a 90° clockwise angle. Make CR = CX Y Repeat the process to find Y and Z

  6. Spin It When will the image exactly overlap the pre-image? 30° clockwise 60°clockwise 90°clockwise 120°clockwise If a figure can be rotated onto itself with an angle or rotation between 0° and 360 °, the figure has rotational symmetry.

  7. Try It Identify the figure(s) that have rotational symmetry and the clockwise angles of rotation between 0° and 360° that cause the image and pre-image to overlap.

  8. Definitions • If a figure can be rotated about some point onto itself through a rotation of between 0° and 360°, then it has rotational symmetry. • A design with rotational symmetry is a rosette. • A figure that can be rotated onto itself through an angle of 180° has point symmetry. • A rotation of 180° is also known as a half-turn.

  9. What is rotational symmetry? If a figure can be rotated onto itself with an angle or rotation between 0° and 360 °, the figure has rotational symmetry. How do you identify a figure that has rotational symmetry? If a figures has rotational symmetry, the clockwise angles of rotation between 0° and 360° will cause the image and pre-image to overlap.

  10. Assignment 3-2A p. 182, 1-15

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