March 12, 2018warm-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]
March 12, 2018
Acircle = π r2
Area of a circle = π radius2
Area of a circle
** Remember to follow order of operations (do exponents before you multiply)
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?
March 12, 2018
Sector of a Circle
Area of sectorArea of circle
degrees in arc360˚
=
- A region bounded by 2 radii of the circle and their intercepted arc.
sector APB
Hint: May need to find area of circle first!
3. Find the area of the sectors formed by ∠HJK.
H
˚
m
March 12, 2018
Assignment:7.9 worksheet
Geometry 7.9 Area of circles and sectors Wksht Answers1. 78.5 cm2 2. 200.96 ft2 3. 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. ≈ 4 m
12. 21.5 cm2 13. 220.16 cm2
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