lesson 1.4 - polygons geometry homework: lesson 1.4/1-26 all assignment from my web page: view ppt...
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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
Examples of polygons:
Convex Polygon Concave
Polygon
Not Polygons
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.
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
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
Polygons are classified according to the number of sides they have.
*A polygon must have at least 3 sides .
Can a slice of pizza be considered a polygon? Explain.
Special Names for Polygons
*n stands for number of sides.
23 23-gon
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
DiagonalThe diagonal of a polygon is a
line segment linking two non-adjacent vertices.
*The diagonals are indicated with dashed lines.
Adjacent – next to
Diagonals in a Polygon
Polygon Number of diagonals
Triangle (3) 0
Quadrilateral (4) 2
Pentagon (5) 5
Octagon (8)
Decagon (10)
n
…
2
3nn*n stands for
number of sides.
20
35
Equilateral Polygon
Equilateral polygons are polygons in which all sides have equal lengths
Equiangular Polygon
Equiangular polygons are polygons in which all angles have equal measures
Regular Polygon:
A regular polygon is a polygon that is equilateral AND equiangular
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