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

4. Find the area of ⨀C

5. Find the area of the shaded region.

6 ft

18 ft

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