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Circles and More Symmetry

Circles and More Symmetry. Slideshow 38, Mathematics Mr Richard Sasaki Room 307. Objectives. Check homework! Learn and recall some circle properties Understand how to find lines of symmetry about a pair of intersecting circles

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Circles and More Symmetry

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  1. Circles and More Symmetry Slideshow 38, Mathematics Mr Richard Sasaki Room 307

  2. Objectives Check homework! Learn and recall some circle properties Understand how to find lines of symmetry about a pair of intersecting circles Complete shapes about set lines of symmetry and rotational symmetry

  3. Compass Warning! For the next few lessons, you will need a compass, a ruler and a regular pencil. Please bring one. If you don’t own a compass, please buy one (you can buy them at 100円 shops). You will need one for the test as well. If for whatever reason you can’t, please let me know as soon as possible.

  4. The Circle Circles can be very complicated things. That’s why we have many words and definitions that we need to know. Let’s learn a few. Centre (origin) Radius Tangent

  5. Diameter The Circle Chord Sector Centre (origin) Radii (plural of radius) Central angle Arc length

  6. 1. parallel, tangents, 90o, perpendicular, 2 Answers different, sizes, tangents, parallel, 0 (no rotational symmetry) 2. 3. It’s regular. No.

  7. We know that a line of symmetry is… Lines of Symmetry A line of reflection where the shape appears the same but reflected on the other side. Does a line of symmetry imply congruence for both sides? Yes. If we split a shape into two along a line of symmetry, both pieces are congruent.

  8. Is the opposite true? Does a line of congruence mean that this is also a line of symmetry? Lines of Symmetry Of course not! We showed this last lesson. These triangles are congruent (same size, same shape). But this certainly isn’t a line of symmetry!

  9. Let’s treat the line of congruence on the rectangle as a line of symmetry. Lines of Symmetry How would the rest of this shape look? It’s a kite!

  10. We can also do the same process with rotational symmetry. Rotational Symmetry Complete the diagram so that the final shape has a rotational symmetry of order 2. 1 2 Order of Rotation

  11. 2 Order of Rotation Answers

  12. 2 Order of Rotation Answers 4

  13. 4 2 Order of Rotation Answers

  14. 2 Order of Rotation Answers 4 8

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