Section 8­7: Circumference and Area of Circles
Essential Question: How do I find the circumference and area of a circle?
Opener: Parts of the Circle
diameter
radius radii
circumference
Mar 18­1:14 PM
Concept 1: Circumference of a Circle
Area Formulas:
Card:
Square
Rectangle
Triangle
Parallelogram
Rhombus
Trapezoid
Circumference of a Circle:
Mar 18­1:20 PM
1
Let's try the Checkpoint Excercises on p. 453 #1­3
Mar 18­1:40 PM
Concept 2: Area of a Circle
Area Formulas:
Card:
Square
Rectangle
Triangle
Parallelogram
Rhombus
Trapezoid
Circumference of a Circle:
Area of a Circle:
Mar 18­1:43 PM
2
Let's try the Checkpoint Excercises on p. 454 #4­6
Mar 18­1:44 PM
Closure: Area of a Sector
Central Angle: An angle whose vertex is the center of the circle and formed with 2 radii.
Sector of the Circle: A region of the circle formed by a central angle. It is a portion of the circle.
Mar 18­1:45 PM
3
To find the area of a sector, we can use a proportion:
Area of the Sector
Measure of the Central Angle
=
Measure of Entire Circle
Area of the Entire Circle
(Always 360 )
Let's try Checkpoint Excercises p. 455 #7, 8 together.
Mar 18­1:59 PM
Try Checkpoint Excercises p. 455 #9­11 on your own!
Mar 18­2:04 PM
4
8­7 Homework: p. 455­457 #1­19 odd, 25­35 odd
Chapter 8 Review: p. 460­463 #1­40
Additional Practice If Needed:
Quiz 1 p. 423
Quiz 2 p.437
Quiz 3 p. 459
Mar 18­2:05 PM
Concepts you need to know for your Chapter 8 Test:
*Convex/Concave Polygons
*Equilateral/Equiangular/Regular Polygons
*Sum of the interior angles of a polygon
*Find 1 interior angle of a regular polygon
*Sum of the exterior angles of a polygon
*Find 1 exterior angle of a regular polygon
*Find the area/find a missing dimension of a
Square
Rhombus
Rectangle
Trapezoid
Triangle
Circumference of a Circle
Parallelogram
Area of a Circle
Area of a Sector
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5
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6
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7
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8
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Attachments
Circumference of a Circle.gsp