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GBK Geometry

GBK Geometry. Jordan Johnson. Today’s plan. Greeting Warm-up & Puzzle Lesson: Polygons Homework / Questions Clean-up. Reptiles as Polygons – M.C. Escher. From paper to paving. Polygons. Again? Didn’t we define them already? Our previous definition:. Polygons.

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GBK Geometry

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  1. GBK Geometry Jordan Johnson

  2. Today’s plan • Greeting • Warm-up & Puzzle • Lesson: Polygons • Homework / Questions • Clean-up

  3. Reptiles as Polygons – M.C. Escher

  4. From paper to paving

  5. Polygons • Again? Didn’t we define them already? • Our previous definition:

  6. Polygons • Again? Didn’t we define them already? • Our previous definition: • A mumble mumblemumblemumblebounded by mumble mumblemumblemumble.

  7. Polygons • Again? Didn’t we define them already? • Our previous definition: • A 2-D figure bounded by line segments.

  8. Polygons • Again? Didn’t we define them already? • Our previous definition: • A 2-D figure bounded by line segments.

  9. Polygons • Again? Didn’t we define them already? • Our previous definition: • A 2-D figure bounded by line segments.

  10. Polygons • OK…here’s the “official” definition from the book: • A polygonis a connected set of at least three line segments in the same plane, such that each segment intersects exactly two others, one at each endpoint. • Why so complicated? • Avoid self-crossing polygons. • Avoid using terms we haven’t defined. • Break the definition down into isolated facts.

  11. Examples and Non-Examples • Sketch 2 example polygons that fit our definition. • Sketch figures that fail to be polygons, in these ways: • Have “sides” that aren’t line segments. • Have fewer than 3 line segments. • Aren’t entirely contained in one plane. • Have segments intersecting more than 2 others. • Have segments intersecting at points other than their endpoints.

  12. Polygons • The bounding segments are sides. • The sides’ intersections are vertices. • Abbreviating polygon names: name the vertices in order. • For example,“Polygon ABCDE”:

  13. Polygons • Name the vertices of the two polygons you drew earlier. • Write the name of each polygon. • (Use its side-based name, e.g. “pentagon PQRST”, if you can.)

  14. Assignments • Asg #27: From Ch. 4 Lesson 2 (pp. 141-144): • Exercises #1-7, 20-24, 37-54. • Bonus: Set III • Due Thursday, 11/7 (per. 1-2) or Friday, 11/8 (7). • Journal #9 – also due Thu/Fri. • Unit 3 Test Corrections – due Tuesday, 11/13. • Center of the circle?

  15. Puzzle Find the center.

  16. Clean-up / Reminders • Pick up all trash / items. • Push in chairs (at front and back tables). • See you tomorrow!

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