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Lesson 10­1 Circles and Circumference with answers.notebook
April 08, 2015
Questions/Main Ideas Lesson 10­1 Circles and Circumference
circle ­ the locus or set of all points in a plane equidistant from a given point called the center
(circles are named by their center point ex: C)
Questions/Main Ideas Examples
1.
a.
Name the circle.
b.
Name a radius of the circle.
c.
Name a chord of the circle.
d.
Name a diameter of the circle.
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Lesson 10­1 Circles and Circumference with answers.notebook
Questions/Main Ideas
April 08, 2015
Radius and Diameter Relationships
If a circle has a radius r and diameter d, the following relationships are true.
d
2
Radius Formula:
r = Diameter Formula: d = 2r
Questions/Main Ideas 2.
1
or r = d
2
Circle R has diameters ST and QM.
a.
If ST = 18, find RS.
b.
If RM = 24, find QM.
c.
If RN = 2, find RP.
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Lesson 10­1 Circles and Circumference with answers.notebook
Questions/Main Ideas
April 08, 2015
Circle Pairs
1. Two circles are congruent if and only if they have congruent radii.
2. All circles are similar.
3. Concentric circles are coplanar circles that have the same center.
Questions/Main Ideas
The Intersection of Two Circles
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Lesson 10­1 Circles and Circumference with answers.notebook
April 08, 2015
The diameters of X, Y, and Z are 22 millimeters, 16 millimeters, and 10 millimeters, respectively.
Questions/Main Ideas 3.
a.
b.
Find EZ.
Find XF.
Questions/Main Ideas Circumference ­ the distance around a circle (often represented by letter C)
pi (π)­ the ratio of circumference to diameter
Circumference
If a circle has diameter d or radius r, the circumference C equals the diameter times pi or twice the radius times pi. C = πd or C= 2πr
Area of a Circle
The area A of a circle is equal to π times the square of the radius r.
A = πr2
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Lesson 10­1 Circles and Circumference with answers.notebook
April 08, 2015
Cherry pie is delicious!
Questions/Main Ideas
C = π d
Apple pies are too!
A = π r2
Questions/Main Ideas Example 4
a.
Find C if r = 13 inches.
b.
Find C if d = 6 millimeters.
c.
Find d and r to the nearest hundredth if C = 65.4 feet.
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Lesson 10­1 Circles and Circumference with answers.notebook
April 08, 2015
Questions/Main Ideas Example 5
Find the exact circumference of K.
Questions/Main Ideas
a.
3√2π
b.
6π
c.
6√2π
d.
12π
A polygon is inscribed in a circle if all of its vertices lie on the circle.
A circle is circumscribed about a polygon if it contains all of the vertices of the polygon.
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Lesson 10­1 Circles and Circumference with answers.notebook
April 08, 2015
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