2. You will find the areas of circles and composite figures as well as find areas of sectors.

3. Let’s look at some theorems. 10-11 Area of a Circle The area of a circle is the product of π and the square of the radius. O r A = π r ²

4. Example: How much more pizza is in a 12-in-diameter pizza than in a 10-in. pizza? r = 5 A = π(5) 2 A = 25π A = 36 π – 25π A = 34.5 in 2 more r = 6 A = π (6) 2 A = 36π

5. Here come more theorems. 10-12 AREA OF A SECTOR THE AREA OF A SECTOR IS THE PRODUCT OF THE RATIO MEASURE OF THE ARC AND THE AREA OF THE CIRCLE 360 r R S O A = m RS 360 (πr²)(πr²) (

6. Example: Find the area of the sector of the slice of pizza. 72 0 20 cm A = m RS 360 (πr²)(πr²) ( R S A = m 72 360 ( π20²) ( A = 80π cm² A = 251.33 cm²

7. Here comes a term. Segment of a Circle A part of a circle bounded by an arc and the segment joining its endpoints. Area of sector – Area of triangle = Area of segment R S O segment of a circle

8. EXAMPLE: Find the area of the shaded segment. R S O 10 in A = m RS 360 (πr²)(πr²) ( A = m 90 360 ( π10²) ( A = 1 / 4 (100) π A = 25 π A = 1 / 2 bh A = 1 / 2 (10)(10) A = 1 / 2 (100) A = 50 A = 25 π – 50 A = 28.53 in 2

9. Assignment Workbook Page 451 all