Geometry 7.9 Day 1 Area of Circles & Sectors

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

Acircle = π r2

Area of a circle = π • radius2

Area of a circle

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

- amount of space covered by the circle (amount of squared units ⇒ units2)

The diameter of a circle is 30 cm. Find the area. 1.

2. The area of a circle is 113.04 yd2. What is the radius?

3. The area of a circle is 49π ft2. What is the diameter?

4. Find the area of the shaded region.

6 ft

18 ft

Area of sectorArea of circle

degrees in arc360˚

=

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

sector APB

Hint: May need to find area of circle first! A = π r 2

part whole

5. Find the area of the sector (the outlined region). Round to nearest hundredth. Area of sector

Area of circledegrees in arc

360˚=

6a. Find the area of the sector (the outlined region). Round to nearest hundredth.

b. Find the area of the "other" region.

Area of sectorArea of circle

degrees in arc360˚

=

Assignment:7.9 Day 1 worksheet

Geo 7.9 Day 1 Area of circle and sectors Wksht Answers1. 153.86 2. 314 mi2

3. 8 4. 12, 24

5. 21.5 cm2 6. 220.16 cm2

7. 63.32 mi2 8. 235.5 cm2

9. 70.65 mi2 10. 225.55 ft2 , 31.79 ft2

11. (x – 6)2 + (y + 1)2 = 100

12. Center (–4, 0), radius = 7

13. x = 26, y = 48 14. x = 14