Polygons

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5-4
Polygons
Warm Up
Problem of the Day
Lesson Presentation
Pre-Algebra
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Warm Up 1. How many sides does a hexagon
have? 2. How many sides does a pentagon
have? 3. How many angles does an octagon
have? 4. Evaluate (n 2)180 for n 7.
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5
8
900
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Learn to classify and find angles in polygons.
A polygon is a closed plane figure formed by
three or more segments. A polygon is named by the
number of its sides.
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Polygon
Number of Sides
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Find the sum of the angle measures in a hexagon.
Divide the figure into triangles from one vertex.
4 triangles
4 180
720
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Find the sum of the angle measures in a octagon.
Divide the figure into triangles from one vertex.
6 triangles
6 180
1080
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Find the sum of the angle measures in a heptagon.
Divide the figure into triangles from one vertex.
5 triangles
5 180
900
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The pattern is that the number of triangles is
always 2 less than the number of sides. So an
n-gon can be divided into n 2 triangles. The
sum of the angle measures of any n-gon is 180(n
2). All the sides and angles of a regular
polygon have equal measures.
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Find the angle measures in the regular polygon.
6 congruent angles
6x 180(6 2)
6x 180(4)
6x 720
x 120
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Find the angle measures in the regular polygon.
4 congruent angles
4y 180(4 2)
4y 180(2)
4y 360
y 90
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Find the angle measures in the regular polygon.
5 congruent angles
a
5a 180(5 2)
a
a
5a 180(3)
5a 540
a
a
a 108
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(No Transcript)
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Give all the names that apply to the figure.
quadrilateral
parallelogram
rectangle
rhombus
square
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Give all the names that apply to the figure.
quadrilateral
parallelogram
rhombus
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Give all the names that apply to the figure.
quadrilateral
A.
parallelogram
rectangle
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Give all the names that apply to the figure.
B.
quadrilateral
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Lesson Quiz Part 1
1. Find the sum of the angle measures in a
quadrilateral. 2. Find the sum of the angle
measures in a hexagon. 3. Find the measure of
each angle in a regular octagon.
360
720
135
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Lesson Quiz Part 2
4. Write all of the names that apply to the
figure below.
quadrilateral, rhombus, parallelogram
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Homework

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