1. Area of Regular Polygons Teacher Notes
Area = ½ (apothem)(perimeter)
Vocabulary:
Apothem
10/28/10
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2. 2-7 Solving Equations With Algebra Tiles powerpoint
Learning Target
I can find the area of regular polygons.
What is a regular polygon?
M2.3.K Know, prove, and apply theorems about properties of quadrilaterals and other polygons.
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Launch
How do you find the area of a triangle
Find the measure of one interior angle of a regular hexagon.
Find the area of the triangle.
A = ½ bh
((n – 2)180)/n
(( 4)180)/6 = 60
h = 4(tan 54) =
A = ½ (1.3764) (8)
= cm^2
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Explore
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Equilateral Triangle
Find the area of the equilateral triangle.
About 27.7 cm^2
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Equilateral Triangle
Explain the process you used to find the area.
Use to find height.
A = ½ (8)(4 sqrt 2)
Or tan 60
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Regular Hexagon
Find the area of the regular hexagon.
About cm^2
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Regular Hexagon
Explain the process you used to find the area.
About cm^2
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It’s the Write Time
What does the process of the find the areas of the triangle and hexagon have in common?
Debrief the class.
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Regular Octagon
Find the area of the regular hexagon.
About cm^2
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Regular Octagon
Explain the process you used to find the area.
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Regular Pentagon
Find the area of the regular hexagon.
About cm^2
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Regular Pentagon
Explain the process you used to find the area.
Watch for the methods they used.
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It’s the Write Time
What do the processes of the find the areas of the hexagon, octagon and pentagon have in common?
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15. How does this formula match your process?
Area of a Regular Polygon
The area of a regular polygon is given by the formula below.
Area = (½)(apothem)(perimeter)
How do we find the apothem?
apothem = ½ (n)(tan (1/2 interior angle)
Debrief the class.
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16. Team Practice Use the formula Area = (½)(apothem)(perimeter)
Find the area of a regular decagon with side length of 8 cm.
Find the area of a regular hexagon with side length of 8 cm.
a =
Area = cm2
a =
Area = cm2
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2-7 Solving Equations With Algebra Tiles powerpoint
Learning Target 5 3 1 2 4
Did you hit the target? I can find the area of regular polygons.
Rate your understanding of the target from 1 to 5.
5 is a bullseye!
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Practice
Area of Regular Polygons
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Ticket Out
Find the area of a regular sided polygon with sides 8 cm.
Interior angle = 150
a = ½ (8) tan(75) =
Area = cm2
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