Copyright by Holt, Rinehart and Winston s2

Name______Date______Class______12.3 Sector Area and Arc Length

In Exercises 1 and 2, fill in the blanks to complete each formula. 1. The area of a sector of a circle with radius r and central angle m° is A  ______. 2. The length of an arc with central angle m° on a circle with radius r is L  ______.

Find the area of each sector. Give your answer in terms of  and rounded to the nearest hundredth.

sector BAC sector QPR ______

Different animals have different fields of view. Humans can generally see a 180° arc in front of them. Horses can see a 215° arc. A horse and rider are in heavy fog, so they can see for only 25 yards in any direction. Round your answers to Exercises 5 and 6 to the nearest square yard. 5. Find the area of the rider’s field of view. ______6. Find the area of the horse’s field of view. ______

Complete Exercises 7–9 to find the area of segment KJL. 7. Find the area of sector KJL. Give your answer in terms of . ______8. Find the area of KJL. ______9. Subtract the area of KJL from the area of sector KJL to find the area of segment KJL. Round to the nearest hundredth. ______

Find each arc length. Give your answer in terms of  and rounded to the nearest hundredth.

10. 11.

XY ______MN ______

Reteach 3 m  m  1. r   2. 2r   1. 63° 2. 117° 360  360  3. 130° 4. 140° 3. 9 mm2; 28.27 mm2 5. 75° 6. 225° 4. 27 mi2; 84.82 mi2 5. 982 yd2 7. 88° 8. 21 6. 1173 yd2 7. 25 in2 9. 16.0 10. 30.0 8. 50 in2 9. 28.54 in2 Challenge 10. 4 cm; 12.57 cm 11. 3 km; 9.42 km 1. 86° 2. 47° Practice B 3. 43° 4. 14 cm 1. sector BAC 126  mm2; 395.84 mm2 AD 5. a. sin 43°  2. sector UTV 30  in2; 94.25 in2 14 3. sector KJL  ft2; 3.14 ft2 b. AD  9.5 cm 4. sector FEG 100 m2; 314.16 m2 c. AB  19.1 cm 5. 4.54 in2 6. 10.96 km2 6. 1.9 in. 7. 3.0 m 7. 24.47 yd2 8. 0.29 cm2 8. 1.3 ft 9. 9. 9.83 mi2 10.  ft; 3.14 ft 骣轾n ℓ = d 琪sin 琪犏 p 桫臌2 11. 14 m; 43.98 m 12. mi; 1.57 mi 2 Students’ answers may vary slightly. 13. 10 mm; 31.42 mm 10. S  5.9 in. 11. P  29.4 in. 12. a  4.1 in. 13. A  59.4 in2 Practice C 14. Formulas may vary in form. 1. Possible answer: The area of a 1骣轾 180鞍骣轾 180 sector of a circle with radius r and central A= nd 2 琪cos 琪 sin 琪犏琪犏骣m 4 桫臌n 桫臌 n angle m is A  r2 琪 . Half this area is 桫360 Problem Solving 骣m r2 琪 . The measure of the segment 1. 270° 2. 72° 桫720 3. 154.8° 4. 115.2° cannot be calculated directly. But if the segment has half the area of the sector, 5. C 6. G then the triangle must have the other half of 7. D the area, and the area of the triangle can be calculated. The height of the triangle is r cos Reading Strategies 骣m 琪 , and the length of the base is 2r sin 1. 60° 2. 360° 桫2 3. central angles 4. 32° 骣m bh 琪 . The area of the triangle is or r2sin 5. 263° 6. 328° 桫2 2 7. 295° 8. 32° 骣m 骣m 琪 cos 琪 . Set this equal to the area of 9. 65° 桫2 桫2 SECTOR AREA AND ARC LENGTH half the sector:

Practice A