Desmos Activity https teacher desmos comactivitybuilderc ustom58 d

Desmos Activity • https: //teacher. desmos. com/activitybuilder/c ustom/58 d 92 ba 29623 f 50 ba 8 d 7 f 2 af

11. 3: Areas of Circles and Sectors

Check Homework •

Arc Length/ Sector Area HW •

Area of a Circle

Ex. 1: MANUFACTURING An outdoor accessories company manufactures circular covers for outdoor umbrellas. If the cover is 8 inches longer than the umbrella on each side, find the area of the cover in square inches.

Ex. 2: Find the radius of a circle with an area of 58 square inches.

Sector - region of a circle bounded by a central angle and its intercepted major or minor arc. - Ex. A slice of pizza. - It is a fractional part of the circle’s area. Area of a Sector:

Ex. 3: A) PIE A pie has a diameter of 9 inches and is cut into 10 congruent slices. What is the area of one slice to the nearest hundredth? B) PIZZA A pizza has a diameter of 14 inches and is cut into 8 congruent slices. What is the area of one slice to the nearest hundredth?

Brain Break Count to 21 • Goal: Count from 1 to 21 as a class without having two people talk at the same time • You must have your eyes closed • If two people talk at the same time, you must start over • Anyone can start and say any number

You Try: Find the area of the shaded sector. Round to the nearest tenth. a) b)

5. The area of a circle is 225π square inches. Find the area of the sector whose central angle is 45°. 6. The central angle of a sector is 60° and the area of the circle is 144π. What is the area of the sector? 7. A circle has a radius of 12. Find the area of the sector whose central angle is 120°.

8. Find the radius of a circle which has a sector area of 9π whose central angle is 90°. 9. The central angle of a sector is 72° and the sector has an area of 5π. Find the radius. 10. Find the measure of the central angle of a sector if its area is 5π and the radius is 6.

Written Summary • Helping You Remember: A good way to remember something is to explain it to someone else. Suppose Jimmy is having trouble remembering which formula is for circumference and which is for area. How can you help him out?