Geometry_7.9_March 14

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warm-up after 7.8:

1. Find the radius. 2. Find the length of AB

3. Find m QR

Geometry 7.9 Area of Circles & Sectors

Learning Target:I can evaluate the area of circles & sectors. [G.C.5]

Geometry_7.9_March 14

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Area of a circle = π radius2

Area of a circle

** Remember to follow order of operations (do exponents before you multiply)

Acircle = π r2

The diameter of a circle is 11cm. Find the area. 1.

2. The area of a circle is 158.3 yd2. What is the diameter?

diameter = 2 x radius

= 14.2 yds

Geometry_7.9_March 14

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Sector of a Circle- A region bounded by 2 radii of the circle and their intercepted arc.

sector APB

Area of sector degrees in arc

Area of circle 360˚=

3. Find the area of the sectors formed by ∠HJK.H

˚

m

Area of Blue Sector

Area of Red Sector

Geometry_7.9_March 14

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4. Find the area of C.

5. Find the area of the shaded region.

6 ft

18 ft

3 circles in total

Area of circles = Ans.

Geometry_7.9_March 14

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Assignment:7.9 worksheet

Geometry Name ______________________________ Pd. ___ 7.9AreaofCircles&Sectors Findtheareaofthecirclewiththegiveninformation.Roundtonearesthundredth.Show all work!1.radius=5cm 2.diameter=16ft 3.circumference=72.22mArea=_____________ Area=_____________ Area=_____________Determinetheradiusofthecirclewiththegivenarea.Roundtonearesthundredth.Show all work!4.Area=25𝜋cm2 5.Area=48ft2 Radius=_____________ Radius=_____________Findtheareaoftheshadedsectors.Roundtonearesthundredth.Show all work!6. 7. 8. Area=_____________ Area=_____________ Area=_____________Usethediagramtofindtheindicatedmeasure.Roundtonearesthundredth.Show all work!9.Areaof⊙𝑀=_____________ 10.Areaof⊙𝑀=_____________ 11.Radius=_____________

Findtheareaoftheshadedregion.Roundtonearesthundredth.Show all work!12. 13. Area=_____________ Area=_____________ 14.Findthecircumference,arclength,areaofthecircleandareaofthesector.Show all work! Circumference=_________ArcLength=__________Areaof⊙=_____________Areaofsector=___________Review.15.Writetheequationofacirclewithcenter(6,–1)andradiusof10.________________________________________________16.Theequationofacircleis(x+4)2+y2=49.Thecenterwouldbe______________andtheradiuswouldbe________.Findthefollowingvalues.Show all work!17. 18.

x=_______ x=_______19. 20. 21.

x=_______

! mAB! =________˚ x=_______ y=_______

210˚

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Geometry 7.9 (Area of circles and sectors) Worksheet Answers1. 78.5 cm2 2. 200.96 ft2 3. (r ≈ 11.5) A ≈ 415.27 m2

4. 5 cm 5. 3.9 ft

6. 52.3 in2 7. 126.04 m2 8. 602.88 ft2

9. 84.02 m2 10. 66.04 cm2 11. (area ≈ 50) r ≈ 4 m

12. 21.5 cm2 13. 220.16 cm2

Area of Square – Area of Circle Area of Square – Area of 16(Circles)

14. C = 37.68 ft, arc length = 21.98 ft,

Area of ⨀ = 113.04 ft2, Area sector = 65.94 ft2

15. (x – 6)2 + ( y + 1)2 = 100

16. (–4, 0), r = 7

17. 110˚ 18. 14

19. 120˚ 20. 61˚ 21. x = 26, y =48