Lesson 1.4 - Polygons
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Transcript of Lesson 1.4 - Polygons
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Lesson 1.4 - Polygons
Geometry Homework: Lesson 1.4/1-26 allAssignment from my web page:
View PPT “Conjectures: aka Theorems and Postulates”.Answer the ‘Time to Ponder’ questions/1-16
(on white lined paper-no fringe)Due: Wednesday, October 2
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Examples of polygons:
Convex Polygon Concave
Polygon
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Not Polygons
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Polygon• Means: “many-angled”• A polygon is a closed figure formed
by a finite number of coplanar segments
• Each segment intersects only at each endpoint.
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Two Types of Polygons:1. Convex: If diagonals are drawn
from the vertices of a polygon, all will be on the interior of the polygon
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2. Concave: If diagonals are drawn from the vertices of a concave polygon, at least one diagonal will be exterior to the polygon.
Visually, the polygon looks caved-in
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Polygons are classified according to the number of sides they have.*A polygon must have at least 3 sides
.
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Can a slice of pizza be considered a polygon? Explain.
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Special Names for Polygons
*n stands for number of sides.
23 23-gon
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Naming a Polygon
Polygon ABCDE • Begin at any point• Follow the path of
the polygon either clockwise or counterclockwise
• MUST stay in order– Polygon Names
• DCBAE• AEDCB• CDEAB….
B
A
E
D
C
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DiagonalThe diagonal of a polygon is a
line segment linking two non-adjacent vertices.
*The diagonals are indicated with dashed lines.
Adjacent – next to
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Diagonals in a PolygonPolygon Number of
diagonalsTriangle (3) 0
Quadrilateral (4) 2
Pentagon (5) 5
Octagon (8)
Decagon (10)
n
…
2
3nn*n stands for
number of sides.
20
35
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Equilateral PolygonEquilateral polygons are polygons in which
all sides have equal lengths
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Equiangular Polygon
Equiangular polygons are polygons in which all angles have equal measures
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Regular Polygon:A regular polygon is a polygon that
is equilateral AND equiangular
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Try This
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N
GAX
E H
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