20110908090313323 - Chapter 2 Differentiation sin x If the...

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Unformatted text preview: Chapter 2 Differentiation sin x If the function f(x) = ——- Were continuous at 0, then it would be simple to compute x the limit at 0; we would just substitute x = 0. However, since the denominator is x,‘ f (x) is not even defined at x = 0. We investigate this limit numerically and graphically. iimit Nim‘ierit‘ally limit Grapi'iieally YA ‘ihnology x 1.5 — nnecti0n ‘ 0.95885 0.97355 . * 098507 Use the TABLE function I I 099335 and the graph to 0.99833 determine 0.99998 . cosx — 1 hm —-——-. 0.99998 HO X 0.99833 Explain why we cannot . 0.99335 use the continuity . 0.98507 properties to determine - 0.97355 this limit. . 0.95885 We can see from both the table and the graph that . sin x lnn = l. Xe O x The other trigonometric limit needed in Section 2.5 is . cosx - 1 11m -——— = 0. x—>0 x This limit is investigated in the Technology Connection located in the margin, and it is investigated algebraically in Section 2.2. Exercise if Determine whether each of the following is continuous. 1. 2. 1pute ' is x, .cally. , and Use the graphs and functions in Exercises 1—4 to answer each of the following. 2.1 5. a) Find lim+ f(x), lim_ f(x), and lim f(x). x—>1 xel X—>1 b) Find f(1). c) Is f continuous at x = 1? (1) Find X13132 f(x). e) Find f(—2). f) Is f continuous at x = —2? 6. a) Find x131; g(x), Xl_i>rr11_ g(x), and g(x). b) Find g(1). c) Is g continuous at x = 1? (1) Find x1_i)rn2 g(x). e) Find g(—2). f ) Is g continuous at x = —2? 7. 21) Find h(x). b) Find 11(1). (2) Is 11 continuous at x = 1? (1) Find hm2 h(x). x—>— e) Find h(-—2). f) Is It continuous at x = ~2? 8. 20 Find lim t(x). x—>1 b) Find t(1). c) Is t continuous at x = 1? - (1) Find Xl_i>1nz t(x). 6) Find t( ~2). f) Is t continuous at x = —2? In Exercises 9—12, use the graphs to find the limits and answer the related questions. 4—x, 2 a 9. Consider f (x) = { forx 75 1, forx = 1. 3) Find l11111+ f(x). b) Find lim f(x). x-—>l_ c) Find 113i f(x). Limits and Continuity: Numerically and Graphically 10. 11. (1) Find f(1). e) Is f continuous atx = 1? f) Is f continuous at x = 2? Consider f(x) = { 4 — x2, forx as *2, 3, forx = —2. a) Find lit—n2+ f(x). b) Find lirn _ x->~2 c) Find x1392 f(x). d) Find f(—2). e) Is f continuous atx = —2? f) 15 f continuous atx = 1? 81 Refer to the graph off below to determine whether each statement is true or false. y 5 4 3 2 l J__ —2 —1 a) 333+ f(x) =f(0) b) X1351. fix) =f(0) c) 11m+ f(x) = x1315} f(x) x—>0 d) lim+ f(x) = limfi f(x) x—>3 x——>3 e lirn x exists. ) x—90 > f) lim f(x) exists. xa3 g) f is continuous at x = 0. h) f is continuous at x = 3. 82 Chapter 2 12. Refer to the graph of g below to determine whether each statement is true or false. 6‘) X1111; g(x) = g(2) b) x113; g(x) = $0) c) x1351. g(x) = X11321. g(x) d) g(x) exists. e) g is continuous at x = 2. 13. Refer to the graph of f below to determine whether each statement is true or false. b) $11112- f(x) = 0 c) x3132, f(x) = X 3:512. f(x) d) Xl_i>m#2 f(x) exists. e> .132. W) = 2 * g)f(0) = 2 h) f is continuous at x = —2. i) f is continuous at x = 0. j) f is continuous at x = —1. Differentiation 14. Refer to the graph of f below to determine whether each statement is true or false. 21) 1111217 f(x) = 3 b) 1m;+ f(x) = o c) x1331, f(x) = x131;+ fix) (1) f(x) exists. e) f (x) exists. f) 3135 f(x) = M) g) f is continuous at x = 4. h) f is continuous at x = 0. 1) 31313 f(x) = gigs f(x) j) f is continuous at x = 2. 15. Refer to the graph of f below to determine whether each statement is true or false. 20 X133. fix) =f(0) b) x133. f(x) = f(0) c) x1_i)rg+ f (x) = XEIEL fix) d)x1#1911214r f(x) = x1351. f(x) e) f(x) exists. f) f(x) exists. g) f is continuous at x = O. h) f is continuous at x = 2. ether Limits and Continuity: Numerically and Graphically 16. Refer to the graph of g below to determine whether each statement is true or false. a) x1351, g(x) = g(0) b) x1351. g(x) = g(0) c) x1351, g(x) = xlggs g(x) d) lim g(x) exists. x—>O e) g is continuous at x = 0. '1 in: Postage Function. Postal rates are $0.37 for the first ounce and $0.23 for each additional ounce (or fraction thereof). Formally speaking, if x is the weight of a letter in ounces, then p(x) is the cost of mailing the letter, where p(x) = $0.37, ifO < x S 1, p(x) = $0.60, if 1 < x S 2, p(x) = $0.83, if2 < x S 3, and so on, up to 13 oz (at which point postal cost also depends on distance). The graph of p is shown below. Is p continuous at 1? at 1.5? at 2? at 2.01? 18.15 p continuous at 2.99? at 3? at 3.04? at 4? 83 Using the graph of the postage function, find each of the following limits, if it exists. 19. x131, p(x), X11311, 1900. 13311 1200 {20; X11351. p(x). 3351, p(x), i332 p(x) 21>, lim p(x), hm p(x),xl_i)1§6p(x) ,1 « x+2.6‘ x—>2.6+ 22. lim p(x) x—>3 23. lim p(x) x—>3.4 Taxicab Fares. In New York City, taxicabs charge pas~ sengers $2.00 for entering a cab and then $0.30 for each one—fifth of a mile (or fraction thereof) that the cab travels. (There are additional charges for slow traffic and idle times, but these are not considered in this problem.) Formally speaking, if x is the distance traveled in miles, then C(x) is the cost of the taxi fare, where C(x) = $2.00, ifx = o, C(x) = $2.30, ifO < x < 0.2, C(x) = $2.60, no.2 s x < 0.4, C(x) = $2.90, if0.4 s x < 0.6, and so on. The graph of C is shown below y'f‘ o—o 3.4— 3.2 — 0—0 3 _ 2.8 — 2.6 — 0W0 2.4 — y : C(x) 2.2 — 2.— | l I | i > 0.2 0.4 0.6 0.8 1 x 24. 15 C continuous at 0.1? at 0.2? at 0.25? at 0.267? 25. Is C continuous at 2.3? at 2.5? at 2.6? at 3.0? Using the graph of the taxicab fare function, find each of the following limits, if it exists. x—>l 4 . 26. li _C(x),xgr1r/14+ C(x),xli)rri/4 C(x) v 27.x11g12w C(x), hm C(x),xl'1£1(1)‘2C(x) x—>0.2+ 28. Flirt? C(x), X£1316+ C(x), $135.6 C(x) 29. lim C(x) 30. lim C(x) x—>.0.5 x~>0.4 84 Chapter 2 - Differentiation t In a certain habitat, the deer population as a function of time (measured in years) is given in the graph of p below. yA 13 — H 115— y=pm 12 — e——-=—O 9—0 11.5 — 11 -— 0—0 9—0 10.5 log—G I | l I 0.5 1 1.5 2 > t ' 31. Identify each point where the population func- tion is discontinuous. 32. At each point where the function is not continu- ous, identify an event that might have occurred in the population to cause the discontinuity. 33. Find thpp p(t). “' 34. Find blip? p(t). , , The population of bears in a cer- tain region is given by the graph of p below. Time t is measured in months. yA 35 ‘— o——-—-—o 34 — y = ptt) o—-—-° 33 — o————o 32— o———-o 9—0 31 — e—o 30;—=0 l | | |_ i > 0.2 0.4 0.6 0.8 1 t 35. Identify each point where the population func— tion is discontinuous. 36. At each point where the function is not continu~ ous, identify an event that might have occurred in the population to cause the discontinuity. 37. Find lim p(t). t—>0.6Jr 38. Find $1316 p(t). ‘ ln psychology one often takes a cer- tain amount of time t to learn a task. Suppose that the goal is to do a task perfectly and that you are practicing the ability to master it. After a certain time period, what (W tW tW is known to psychologists as an “I’ve got it!” experience 1 occurs, and you are able to perform the task perfectly 39. At what point do you think the “I’ve got it!” experi- ence happens on the learning curve below? 40. Why do you think the curve below is constant for inputs t Z 20? N(t)A H 100 - o—-———— 8 90 — E 80 — 3, % 7o — E E _ LE 8 60 o ,_. 50 — 5% w— ,0 E: 30 — :3 Z 20 :/j 10 — _ ____|_____|___L9 10 20 30 t Time (in hours) Using the graph above, find each of the following lim- its, if it exists. 41. [1136+ N(t),t11)12r6w N(t),t1i)r121O N(t) 42. [Egg N(t), [Egg N(t),tl_1_)r§10 N(t) 43. Is N continuous at 20? at 30? 44. Is N continuous at 10? at 26? 45. Discuss three ways in which a function may not be continuous at a point a. Draw graphs to illustrate your discussion. Use the Continuity Properties C1— C5 to justify that the function is continuous. Then give the limit using the fact that the function is continuous. 46. f(x) = x2 + 5x — 5; 1mg f(x) x% 47. f(x) = 3x3 + 2x2 —~ 9x + 4; lim1 f(x) x——> x x 48. = ,f 75 1; 1' g(x) x - l orx x—1>n-11x — 1 49 () x2 + 9x — 7 . x =—————, ’3 x+ 2 2 + _. forxsté ~2‘,limx——-9x—Z x91 x+ 2 7T 7T 50. tanx,for——<x<——; lim tanx 2 2 x—>7r/4 51.cotx,for0<x<7r; lim cotx x%7r/3 7T 7T , 52. secx, for —— <x < —; hm secx 2 2 raw/6 53. csc x, for O < x < 77; lim csc (x) xew 4 )t be ate It the he 2.2 Limits: Aigebraicaliy 85 OBJECTIVE I Find limits using algebraic methods. the limit. (542}flx) = VXZ + 2x + 4 (Hint: f is a composition 1. x3 + x2 — x w 1 L/ of functions); 59. Xirnl ——————————x3 + 1 55. f(x) = Vsinx,for0 <x < 77; lim Vsinx 1 _ COSX ‘ Wm 60. lim ———— 56. g(x) = sinzx; lim sinzx ’HO 3‘ I“? 77/4 1 tan h 57. g(x) = cos(2x + 3n);xhr7rT1/6 cos(2x + 37r) 61. Illino h 62 1, sinx — x "it? in": n fanny n '* U N; - x1310 x3 ' In Exercises 58—63, use a grapher to determine the 63' hm gal}: limits. Make a table for each and draw the graph. 1160 h 5814 x2+3x—4O ' 13% x2 + 4x — 2.2 Limits: Algebraically Using Limit Principles If a function is continuous at a, we can substitute to find Examing 4 Find lim sz — 3x + 2. x—>0 ,goiniion Using the Continuity Principles, we have shown that polynomials such as x2 — 3x + 2 are continuous for all values of x. When we restrict x to values for which x2 — 3x + 2 is nonnegative, it follows from Principle C5 that sz — 3x + 2 is continuous. Since x2 — 3x + 2 is nonnegative when x = 0, we can substitute to find the limit: lir%Vx2—3x+2=VO2—3-O+2 X% =\/i. aaaaiata 2 Find lim sin(x2 ~ 4). 2092 505mm By the Continuity Principles, we know that x2 — 4 is continuous. There- fore, the composition sin (x2 — 4) is also continuous since the sine function is con~ tinuous. To find the limit, we simply substitute x = 2,. lim2 sin(x2 — 4) = sin(22 — 4) = sin(O) = 0. X'fi Using the fact that many of the usual functions from algebra and trigonome- try are continuous, we can compute many limits by simply evaluating the func- tion at the point in question. It is also possible to use Limit Principles to compute limits. These principles can be used when we are uncertain of the continuity of the function. l the , and .15. 2.2 Find the limit using the algebraic method. Verify using the numerical or graphical method. 1. lim (x2 —~ 3) x—>0 x 5. lim (2x + 5) x—93 . x2 — 25 7. hm i x+~5 x + 5 2. lim (x2 + 4) x—>1 4. lim :4: x—>O x 6. lim (5 — 3x) x—>4 2 — l6 8. lim £—-——— X~>-4 x+ 4 —2 10. lim — x—>—5 x 2.. _ I x x 20 12. hm —— x944 x + 4 Find the limit. Use the algebraic method. 13. 11m5 V3 x2 — 17 X% 15. lim (x + sin x) x—>7r/4 , l+sinx 17.l1m ——.— x—>01—smx . 1 19.)}1_I§12x_2 3 2—4 +2 21. mill—i— x—>27x ~5x+3 4 2+5 —7 22. lim 353; xa-13x —2x+ 1 2+ —6 23.11m¥——— x—>2 x *4 2 “16 24.lim x xa‘txz—x—IZ 25. Ilirno (6x2 + 6x11 + 2112) 1% 26. lim (10x + 511) 11%0 . —2x — h 27' 113%) x2(x + 102 28. lim —_5— h~>0 x(x + h) tan X 29. lim x—>0 x 30. lim x csc x x~>0 14. 111112 ‘\/x2 + 5 X6 16. 11m (cosx + tanx) x—>7r/6 . 1 + cosx 18.11m ————-— 26—20 cosx 20 l' 1 . 1m ———-—-—-—- x—>1(x — l)2 2.2 Limits: Algebraically 91 Find the limit, if it exists. ‘ sinxsin h , sinxcos h — sinx 31. hm — 32. llm ——- h~90 h 1160 h , x2+3x .x2—2x4 33. 11m 2——.—. 34. 11m 2— x—>0x — 2x x—>Ox + 3x . XV; . x + 2c2 35. xlgggc + x2 36. lino xv; x — 2 37. lim ——-——— X_’2 x2 — x — 2 ‘ x2 — 1 38. km X~>~1 x + 1 39 1‘ x2 _ 9 . 1m x—>3 2x — 6 3 2 + 5 — 2 40.11111 ———x x H72 x2 — 3x — 10 '5. N )7. . '. A 4 3‘32 ,. r l t H u l 1.1 l; 4,7 t. 0 ll Further Use 011110 114811? Failure. In Section 2.1, we discussed how to use the TABLE feature to find limits. Consider . Vl+x—1 l1m—-——-———. x—>0 x Input—output tables for this function are shown below. The table on the left uses TblStart = - l and ATbl = 0.5. By using smaller and smaller step values and begin— ning closer to O, we can refine the table and obtain a better estimate of the limit. On the right is an input— output table with TblStart = ~0.03 and ATbl = 0.01. 0.503807 . 0.585786 0.502525 0 ERROR * 0.501256 0.5 0.449490 ERROR 1 ' 0.414214 0.498756 1.5 0.387426 0.497525 2 0.366025 0.490305 92 Chapter 2 - Differentiation It appears that the limit is 0.5. We can verify this by graphing \/1+x—1 y: x and tracing the curve near x = O, zooming in on that portion of the curve. 41. y = W~ 1 x 42. 43. Limit=0.5 44. 45. We see that 46 \/ 1 + — 1 ' lim ————x—" = 0.5. Xflfo x 47 This can be verified algebraically. (Hint: Multiply by 1, ' . \/ 1 + x + 1 usm -—————. g m + 1 48- OBJECTIVES I Compute an average rate of change. I Find a simplified difference quotient. feature and start with ATbl = 0.1. Then move to 0.01, 0.001, and 0.0001. When you think you know the limit, graph and use the TRACE feature to verify your assertion. Then try to verify algebraically. y‘ In Exercises 41—48, find the limit. Use the TABLE 2~ . a 4 11m—-——— a~>'Z\/a2+5—3 , W—l lim——— x—>1 x—l V3—x—\/§ lim x—>0 X hm ______.V4+x— V‘i—X x—>O x x — W x ~ 1 hm ___.__V7+2x—W x—>0 x . 2—\/§ lim—-—- x—>4 4—x . 7— V49—x2 l1m-———-—- x—>O x lim x—>1 2.3 Average Rates of Change Let’s say that a car travels 110 mi in 2 hr. Its average rate of change (speed) is 110 mi/Z hr, or 55 mi/hr (55 mph). On the other hand, suppose that you are on the freeway and you begin accelerating. Glancing at the speedometer, you see that at that instant your instantaneous rate of change is 55 mph. These are two quite different concepts. The first you are prob— ably familiar with. The second involves ideas of limits and calculus. To understand instantaneous rate of change, we first use this section to de— velop a solid understanding of average rate of change. Photosynthesis is the conversion of light energy to chemical energy that is stored in glucose or other organic compounds.1 In the process, oxygen is produced. The following graph approximates the amount of oxygen a plant produces by pho- tosynthesis. Time 0 is taken to be 8 AM. The rate of photosynthesis depends on a number of factors, including the amount of light and temperature. 1N. A. Campbell and].B. Reece, Biology, 6th ed. (Benjamin Cummings, New York 2002). 98 Chapter 2 - Differentiation Eiercisf‘e’éetflgéH For the functions in each of Exercises 1—12, (a) find a) The average growth rate of a typical boy during a simplified form of the difference quotient and his first year of life. (Your answer should be in (b) complete the following table. pounds per month.) b) The average growth rate of a typical boy during his second year of life. c) The average growth rate of a typical boy during his third year of life. d) The average growth rate of a typical boy during his first 3 yr of life. e) When does the graph indicate that a boy’s growth rate is greatest during his first 3 yr of life? 1. f(x) = 7x2 2. f(x) = 5x2 3. f(x) = —7x2 4. f(x) = —5x2 5. f(x) = 7x3 6. f(x) = 5x3 fl 5 4 . = — 8. = — 7 fix) x xx) X 9. f(x) = ~2x + 5 10. f(x) = 2x + 3 11 f(x) = x2 _ x 12 f(x) = X2 + X a, a as: Earthy. Use the graph in Exercise 13 to ' ' estimate: a) The average growth rate of a typical boy during his first 9 mo of life. (Your answer should be in pounds per month.) 13. Gaby. The median weight of boys b) The average growth rate of a typical boy during IS given in the graph below. Use the graph to his first 6 m0 of life estimate:2 ' . c) The average growth rate of a typical boy during his first 3 mo of life. Jig 30 -v tW d) Based on your answers in parts (a)—(c) and 3 25 the graph, estimate what the average growth g rate of a typical boy should be the first few 3;) 20 " weeks of his life. g 10 < "U E 5 ._ Age in months 2Centers for Disease Control. Developed by the National Center for Health Statistics in collaboration with the National Center for Chronic Disease Prevention and Health Promotion (2000). 13 to during :1 be in during during 1nd wth 3W 15. Growth oj‘a Baby. Use the following graph to estimate: M 26 V) g 255 8 D; 25 1:1 '2 24.5 a» 2. OJ 3 a 23.5 g z 23 - 22.5 )1 16 17 18 x Age in months 12 13 14 15 a) The average growth rate of a typical boy between ages 12 mo and 18 mo. (Your answer should be in pounds per month.) b) The average growth rate of a typical boy between ages 12 mo and 14 mo. c) The average growth rate of a typical boy between ages 12 mo and 13 mo. tW (1) Based on your answers in parts (a)—-(c) and the graph, estimate the average growth rate of a typi— cal boy when he is 12 mo old. 16. ilfittpei’ciim‘ifi Dining (111 Himss. The temperature T, in degrees Fahrenheit, of a patient during an illness is shown in the following graph, where t is the time, in days. TA (6 102.5) A 103— ’ 6 102— (4,102) (8,102) "U .E z 101— (3,101) H :3 g 100_ (9.100) g (2, 99,5) (11, 98.6) a 99— 98.6 (1, 98.6) (10, 98.6) 1 1 1 1 1 _1_ 1 1 1 1 1 > 1234567891011t Time (in days) a) Find the average rate of change of T as t changes from 1 to 10. Using this rate of change, would you know that the person was sick? b) Find the rate of change of T with respect to t, as t changes from 1 to 2; from 2 to 3; from 3 to 4; from 4 to 5; from 5 to 6; from 6 to 7; from 7 to 8; from 8 to 9; from 9 to 10; from 10 to 11. tW 17. UN 18. 19. 20. 2.3 Average Rates of Change 99 c) When do you think the temperature began to rise? reached its peak? began to subside? was back to normal? d) Explain your answers to part (c). Memm-y, The total number of words M(t) that a person can memorize in time t, in minutes, is shown in the following graph. M Number of words memorized >. 0 8 16 24 323640 1 Time (in minutes) a) Find the average rate of change of M as t changes from O to 8; from 8 to 16; from 16 to 24; from 24 to 32; from 32 to 36. b) Why do the average rates of change become 0 after 24 min? Average Velocity. A car is at a distance 5, in miles, from its starting point in t hours, given by s(t) = 10t2. 21) Find 5(2) and 5(5). b) Find 5(5) — 5(2). What does this represent? c) Find the average rate of change of distance with respect to time as t changes from t1 = 2 to t; = 5. This is known as average velocity, or speed. Average Velocity. An object is dropped from a certain height. It is known that it will fall a distance 5, in feet, in t seconds, given by s(t) = 16t2. a) How far will the object fall in 3 see? b) How far will the object fall in 5 see? c) What is the average rate of change of distance with respect to time during the period from 3 to 5 see? This is also the average velocity. Gas Mileage. At the beginning of a trip, the odome- ter on a car reads 30,680 and the car has a full tank 100 Chapter 2 Differentiation of gas. At the end of the trip. the odometer reads 30,970. It takes 15 gal of gas to refill the tank. a) What is the average rate of change of the number of miles with respect to the number of gallons? b) What is the average rate of consumption (that is, the rate of change of the number of miles with respect to the number of gallons)? each of two countries at time t, in years. U) 0 O Population (in thousands) (3, 200) of 100 (1, 125) v I | I | 0 1 2 3 4 Time (in years) HY 2) Find the average rate of change of each population (the number of people in the population) with respect to time t as t changes from 0 to 4. This is often called an average growth rate. tW b) If the calculation in part (a) were the only one made, would we detect the fact that the populations were growing differently? Explain. c) Find the average rates of change of each population as t changes from 0 to 1; from 1 to 2; from 2 to 3; from 3 to 4. UN d) For which population does the statement “the population grew by 125 million each year” convey the least information about what really took place? Explain. fr to 2000 is approximated in the graph shown below. Use this graph to answer Exercises 22 and 23.3 3California Department of Fish and Game. . , . 7.3mm; The two curves shown in the following figure describe the number of people in UN tW yi 800,000 — 600,000 400,000 — 200,000 — | | I | g 1850 1900 1950 2000 x 22. Consider the parts of the graph from 1850 to 1860 and from 1890 to 1960. Discuss the differences between these two pieces of the graph in as many ways as you can. Be sure to consider average rates of change. 23. Pick out pieces of the graph where the slopes and shapes are similar and pieces where the slopes and shapes are different. Explain the differences and the similarities. Can you identify historical occurrences that correspond to when the graph changes? Find the simplified difference quotient. 24. f(x) = mx + l) 25. f(x) = ax2 —- bx + c 26. f(x) = ax3 -- bx2 27. f(x) = W ’\ / -_ I __ (Hint: Multiply by 1 using H x 1 x 28. f(x) = x4 29. f(x) = i 30. f(x) = 1 w x 31. f(x) = 1 j: x 32. f(x) = V3 — 2x 33. f(x) = gr; 2x 34. f(x) =x_ l Differentiation 112 Chapter 2 - Technology Connection (continued) To draw a tangent line at x = 70, we go to the home screen and select the TANGENT feature from the DRAW menu. Then we enter Tangent(Y1, 70). We see the graph of f (x) and the tangent line at x = 70. Tangent(Y 1,70) 3000 100 it Some calculators will give answe do not exist. For example, f (x) = M does not have a derivative at EXERCISES For each of the following functions, evaluate the derivative at the given point. Then draw the graph and the tangent line. 1. f(x) = x(100 — x); x= 20,x=37,x=50,x= 90 2. f(x) = —§x3 + 6x2 — 11x — 50; x 5.x O,x 7.x 12.x 15 3. f(x) = 6x2 — x3; x 2,x O,x 2,x 4,x 6.3 4. f(x) = 3cm; x= —2,x= —1.3, x= *O.5,x=0,x= 1, x = 2 tW 5. For the function in Exercise 4, try to draw a tangent line at x = 3 and estimate the derivative. What goes wrong? Explain. rs for derivatives even though they x = 0, but some calculators will give 0 for the answer. Try entering nDeriv(abs(X), X, 0) to see what your calculator does. Set 2.4 In Exercises 1—16: a) Graph the function. h) Draw tangent lines to the graph at points whose x—coordinates are —2, 0, and 1. c) Find f ’ (x) by determining Ilimo h 1‘9 . d) Find f’(—2), f’(0), and f’(1). How do these slopes compare with those of the lines you drew in part (b)? 1. f(x) = 5x2 2. f(x) = 7x2 3. f(x) = —5x2 4.f(x) = —7x2 5. f(x) = x3 6.f(x) = —x3 7.f(x)=2x+3 8.f(x)= —2x+5 f(x + h) —f(x)' 9. f(x) = —4x 11. f(x) = x2 + x 13. f(x) = 2x2 + 3x — 2 14. f(x) = 5x2 — 2x + 7 15. f(x) = 1 16- fix) = ? i X 17. Find f’ (x) for f(x) = mx. 18. Find f’(x) for f(x) = ax2 + bx + c. , 1 and ative. icy 11; lg 19. 20. 21. 22. 23. 24. 2.4 Differentiation Using Limits of Difference Quotients Find an equation of the tangent line to the graph of f(x) = x2 at the point (3,9), at (—1, 1), and at (10, 100). See Example 3. Find an equation of the tangent line to the graph of f(x) = x3 at the point (—2, —8), at (0,0), and at (4, 64). See Example 4. Find an equation of the tangent line to the graph of f(x) = 5/x at the point (1,5), at (—1, ~5), and at (100, 0.05). See Exercise 16. Find an equation of the tangent line to the graph of f(x) = 2/x at the point (*1, —2), at (2,1), and at (10;). Find an equation of the tangent line to the graph of f(x) = 4 — x2 at the point (—1,3), at (0,4), and at (5, —21). Find an equation of the tangent line to the graph of f(x) = x2 — 2x at the point (—2,8), at (1, —1), and at (4, 8). List the points in the graph at which each function is not differentiable. 25. 27. 21:16 Posing , "2ii'§i’iti{??i. Consider the postage func— tion defined on page 83. At what values is the func- tion not differentiable? c, (.1 28. 29. WV 30. 31. 113 'i he Taxicab Shannon. Consider the taxicab func- tion defined on page 83. At what values is the func~ tion not differentiable? Bimini}? "l‘irizyz Prices. Consider the model for major league baseball average ticket prices in Exercise 35 of Exercise Set 1.2. At what values is the function not differentiable? 33w: fiopniatiua. Using the graph below to model the population of deer in California, in which years is the function not differentiable? Explain. y 800,000 600,000 Deer 400,000 200,000 | | i | > 1850 1900 1950 2000 x Year {,Qé'tfrwffi (if iii/index The graph below approximates the weight, in pounds, of a killer whale (Orcinus area)“r The age is given in months. Find all months where the weight function is not differentiable. YA 3500 — 3000 -— 2500 - 2000 1500 1000 500 Weight | l l | | 3 10 20 30 4O 50 60x Age ‘iSeaWorld. Differentiation 41. Consider the function f given by W9 32. Which of the following appear to be tangent lines? fix) 2 x2 — 9 Try to explain why or why not. x + 3 ’ For what values is this function not differentiable? 42—47. Use a grapher to do the numerical differen— tiation and draw the tangent lines in each of Exer- cises 19—24. 48. i , The median weight w of a girl whose age t is between 0 and 36 1110 can be approximated by the function WV 33. In the following figure, use a blue colored pencil w(t) = 0.0006t3 — 0.0484t2 + 1.61t + 7.6, and draw each secant line from point P to the points Q. Then use a red colored pencil and draw a tangent line to the curve at P. Describe what happens. where t is measured in months and w is measured in pounds. Use this approximation to make the following computations for a girl with median y weight.5 Note: Some graphers use only the variables x and y, so you may need to change the variables when entering the function. a) Graph w over the interval [0, 36]. b) Find the equation of the secant line passing , through the points (12, w(12)), and (36, w(36)). Then sketch the secant line using the same axes as in part (a). i c) Find the average rate of growth in pounds per month for a girl of median weight between ages“: 12 mo and 36 mo. (1) Repeat parts (b) and (c) for pairs of points (12, w(12)), and (24, w(24)); (12, w(12)) and (18, w(18)); (12, w(12)) and (15, w(15)). e) What appears to be the slope of the tangent line at the point (12, w(12))? 35100 = é x 1+x 37. f(x) = Vx+h+\/)—c> V X + h + v; 5Centers for Disease Control. Developed by the National Cen— ter for Health Statistics in collaboration with the National i 40. = 3x— Center for Chronic Disease Prevention and Health Promotion V; x + 5 (2000). (Multiply by 1, using 39. f(x) = ...
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This note was uploaded on 01/19/2012 for the course MA 23100 taught by Professor Josephchen during the Fall '11 term at Purdue University-West Lafayette.

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20110908090313323 - Chapter 2 Differentiation sin x If the...

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