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Geo1.4 Polygons Lesson

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• Remind students that we saw vertex last week during our angles lesson!
• Perform this slide together as a class by compiling the polygon’s names on the board.
• Allow students to work independently to find four different ways that this polygon can be named. Then, gather class together to compile list.
• Emphasize the use of pre-fixes to denote the number of sides in the polygon.
• Have students create this chart in their notebook. Have students start by drawing each polygon. Then, have them figure out the number of diagonals by connecting non-consecutive vertices. (up to hexagon – have them do the others as a challenge). Discuss the n-gon and what it represents!
• Geo1.4 Polygons Lesson

1. 1. AIM 1.4 : How can we define and classify polygons with 3 to 12 sides? <ul><li>DO NOW (4 minutes) </li></ul><ul><ul><li>Using our knowledge of a ‘good’ definition, come up with definitions for the following shapes: </li></ul></ul><ul><ul><li>Triangle </li></ul></ul><ul><ul><li>Square </li></ul></ul><ul><ul><li>Rectangle </li></ul></ul>REMINDER! Quiz #1 on MONDAY ! September 9 th , 2009
2. 2. Polygons <ul><li>What are polygons? </li></ul><ul><ul><li>A polygon is a closed figure in a plane, formed by connecting line segments endpoint to endpoint with each segment intersecting exactly two others. </li></ul></ul>Polygons: NOT Polygons:
3. 3. Sides & Vertices <ul><li>Each polygon has sides and vertices. </li></ul><ul><ul><li>Sides are made up of the line segments on the polygon. </li></ul></ul><ul><ul><li>The point in which two sides meet is called a vertex . </li></ul></ul>side side vertex vertex How many sides and vertices does this polygon have?
4. 4. How do we notate polygons? <ul><li>The following polygon needs a name!! </li></ul><ul><ul><li>What can you call it? </li></ul></ul><ul><ul><li>We name a polygon by listing the vertices in consecutive order. </li></ul></ul><ul><li>Polygon MATH </li></ul><ul><li>Polygon ATHM </li></ul><ul><li>Polygon THMA </li></ul><ul><li>Polygon HMAT </li></ul><ul><li>Polygon MHTA </li></ul><ul><li>Polygon HTAM </li></ul><ul><li>Polygon TAMH </li></ul><ul><li>Polygon AMHT </li></ul>
5. 5. Give me a name! <ul><li>Find up to four different ways you can name this polygon: </li></ul>Polygon CRAZY Polygon RAZYC Polygon AZYCR Polygon ZYCRA Polygon YCRAZ Polygon CYZAR Polygon YZARC Polygon ZARCY Polygon ARCYZ Polygon RCYZA
6. 6. Let’s analyze this polygon! consecutive sides consecutive vertices consecutive angles Quadrilateral ABCD 1) What is this polygon’s name? 2) How many sides and vertices are there? 4 sides & 4 vertices 3) Name all of my sides using proper notation. AB, BC, CD, and DA 4) Name all of my angles using proper notation. <ADC, < DCB, < CBA, <BAD 5) Identify my consecutive sides. 6) Identify my consecutive vertices. 7) Identify my consecutive angles. _ _ _ _
7. 7. Diagonals <ul><li>A diagonal of a polygon is a line segment that connects two non -consecutive vertices. </li></ul>Polygon ABCD has two diagonals. Polygon EFIHG has five diagonals. This polygon is CONVEX . This polygon is CONCAVE because one or more diagonals are outside.
8. 8. How many diagonals do I have? <ul><li>Identify how many diagonals does polygon CRAZY have… </li></ul>5 diagonals
9. 9. Classifying Polygons <ul><li>Polygons can be classified by the number of sides it has. </li></ul><ul><li>We use Greek and Latin pre-fixes to name specific polygons. </li></ul><ul><li>For example: </li></ul>Triangle
10. 10. Classifying Polygons In your notes, create this chart to act as a guide to naming polygons. Make sure you include space for the drawings. Draw each polygon with the correct number of sides. Then, find the number of diagonals up to the 6-sided polygon. Try the others as a challenge!! Polygon Name # of Sides # of Diagonals Drawing Triangle 3 Quadrilateral 4 5 6 7 8 9 10 Undecagon 11 Dodecagon 12 n
11. 11. Polygons An Australian 50-cent coin is a dodecagon! The UK 50-pence coin is a heptagon! Don’t forget to draw the polygons! Polygon Name # of Sides # of Diagonals Triangle 3 0 Quadrilateral 4 2 Pentagon 5 5 Hexagon 6 9 Heptagon 7 14 Octagon 8 20 Nonagon 9 27 Decagon 10 35 Undecagon 11 44 Dodecagon 12 54 n -gon n ½n(n–3)
12. 12. Quick Check! <ul><li>Draw a pentagon house with a quadrilateral chimney, three triangular windows, and a hexagonal sun. </li></ul><ul><li>Include additional polygons for extra brownie points!! </li></ul>GO!
13. 13. Ever wonder…? <ul><li>Ever wonder what a 38-gon is actually called? </li></ul><ul><ul><li>A 38-sided polygon is called triacontakaioctagon ! </li></ul></ul><ul><li>How about a 100-gon? </li></ul><ul><ul><li>A 100-sided polygon is called hectogon . </li></ul></ul><ul><ul><li>Find out more: </li></ul></ul><ul><ul><ul><li>http://mathforum.org/dr.math/faq/faq.polygon.names.html </li></ul></ul></ul><ul><ul><ul><li>Go impress your friends! </li></ul></ul></ul>Let’s try to say that one together!
14. 14. Guided Practice <ul><li>Turn to pages 56-57 . Work on #1 – 12 . </li></ul>I’m the polygon robot! What type of polygons is the robot made up of?
15. 15. YES… WE CAN!!!
16. 16. In closing… <ul><li>How do we classify and define polygons? </li></ul><ul><li>How do you find the number of diagonals in a polygon? </li></ul><ul><li>LOOKING AHEAD… </li></ul><ul><ul><li>Tomorrow, we will take a deeper look at 3-sided polygons, or triangles. </li></ul></ul><ul><li>HOMEWORK… </li></ul><ul><ul><li>Complete worksheet. </li></ul></ul>