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Geometry. Agenda 1. ENTRANCE 2. Go over Practice 3. Quiz 4. 3-4 The Polygon Angle-Sum Theorems 5. Practice Assignment 6. EXIT. Practice. Quiz Time Good Luck!!!. Chapter 3. 3-4 The Polygon Angle-Sum Theorems. Polygon.
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Geometry • Agenda 1. ENTRANCE 2. Go over Practice 3. Quiz 4. 3-4 The Polygon Angle-Sum Theorems 5. Practice Assignment 6. EXIT
Quiz Time Good Luck!!!
Chapter 3 3-4 The Polygon Angle-Sum Theorems
Polygon • A closed figure that consists of three or more segments joined at the endpoints and each segment must meet exactly two other segments.
Polygon Terms • 3 sides Triangle • 4 sides Quadrilateral • 5 sides Pentagon • 6 sides Hexagon • 7 sides Heptagon • 8 sides Octagon • 9 sides Nonagon • 10 sides Decagon • 11 sides Undecagon • 12 sides Dodecagon • n sides n-gon
Naming A Polygon • A polygon is named by the number of sides. ex: If a polygon has 5 sides, you use 5 letters. Polygon ABCDE
Types of Polygons • Convex • The diagonals are entirely inside the figure. • Concave • At least one diagonal is partly outside the figure.
Regular Polygon • Remember: equilateral, equiangular • A regular polygon is a polygon that is both equilateral and equiangular.
Theorem 3-9Polygon Angle-Sum Theorem • The sum of the measures of the angles of an n-gon is (n-2)180. ex: This pentagon has 5 sides.
Theorem 3-10Polygon Exterior Angle-Sum Theorem • The sum of the measures of the exterior angles of a polygon, one at each vertex, is 360. ex: This pentagon has 5 sides. The sum of the 5 exterior angles is 360.
Example #1 • Name the polygon. Identify vertices, sides, and angles. Is it concave or convex?
Example #2 • Find the interior angle sum. a. 13-gon b. decagon
Example #3 • How many sides does each polygon have if its interior angle sum is: a. 2700 b. 1080
Example #4 • Find x.
Example #5 • Find y.
Example #6 • Find x.
Example #7 • Find x.
Example #8 • Find x.
Example #9 • How many sides does each regular polygon have if its exterior angle is: a. 120 b. 24
Example #10 • How many sides does each regular polygon have if its interior angle is: a. 90 b. 144
Practice • WB 3-4 # 1-19 • EXIT