管 院 微 積 分 聯 合 教 學 段 考 五 May 06, 2014 考 試 時 間 l20分 鐘 , 題目卷 為三張紙 ,共五頁 ,滿分120分。所有 題目的答 案 都請依題 號順序依序寫在答案卷上,而是非與填充題必須寫在第一頁。答案 卷 務必寫學 號、姓名 ,題目卷不 必繳回。 考試開始 30分鐘後不得入場,開始 40分鐘內不 得離場。 考試期間禁 止使用字 典、計算 機及任何通訊器材,監試 人 員不得回 答任何關 於試題的疑 問。Quest ions are to be an swer ed o n th e answer sheet provided. 是 非 題 True or False (20 poLnts), 請 答 T(Tue)或 F(False)。 每 題 2分 。 ( 不 需 詳列 過 程 , 請依 題 號 順 序依 序 寫 在 答案 卷 第 一 頁上 。 ) F ’ , 玨 y=/(x)h a solution ofa first-order diiferential equation, then,=c.,(x) is also a solution of址 lefirst-order diferential equation, whEre C id any real number. F。 , 9: c、乎 f'j (Sol) 二 c, ( ; 化 ’ r3x+仁 , 手 , g、 6。njf d's. 丫 咎‘-占勺十歹 宁 身 ’ =c、 ( e, 1:r5夕 丰 6x于夕 争clg二fefc于F,d咒 宁齧二3咒’f多咒+ 舌,幸:。‘。“弘* ”亡 州 几/ 彤 >9, 1 -r 2. If y = eTt satisfies the differential equation y" - y' - 3 0y = 0 , th en the va lue of 'r is 6 0r -5. (Sol) yn _ y' _ 30y = (r2 _ r - 30)ert = (r - 6)(r + 5)ert T 3.Ⅱ J =/y. dA , wh ere D is the dis k {X2 +y2 < 1 6}, then I =14 43. 23 (Sol) (jD xfi了(了 ,dA =the volume of the upper half ba with radius 4 and center at (0,0,0). 1 b 4. For any function f, if f(x)dx = 1, then f must be a probability density function on [a, bl. (Sol) - Co \ o e 队 P YO b O \ D ' l ' tA  ̄ U . v \ ct , o v k . 于 \ m O k S I b 乏 y i o\ i - Y l p  ̄ o' t ' x ' Q . 一 5.The differential equation ydx -(蠶十 : r:2y)dy=o is separable (Sol) 化[ 1 +亿l 呵) dx二寸“乎 十 h巳化 , 净teYp1 5。幻r be LH S c。n n 。亡b f se P,Y O, t‘翻 6. A deposit of ¥10, 000 is made into a bank account a nd the ac cou nt e arn s i nte res t at a rate of 3.2% per year, compounded continuously. The balance, B, in the account in t year s s ati sfi es the di ffe rent ial eq uat ion dB /dt = 10, 000 + 0.0 32B . (Sol) dBldt = 0.032B with B(O) - 10000. 7 . The me di an (中位數)of a no rm al d is tr ib ut io n is n e ve r at z er o. (S ol ) Ik k、肌乏d下队n 。干 SC d订O [0 1 Y爿 n 。rr ”q O I Ts C V 7 b “t7 。n ;j 。、 /下頁還有 試題) 2 I f d Q/ d t = 5 Q - 2 0 0 t h e n w h e n Q = 1 0, t h e q u a n t i t y Q w i l l b e d e c r e a s i n g ( S ol ) dQ /d t lo =i o = ( 5 Q - 2 00 )1 0 =i o = - 1 50 < 0 H en c e Q i s de c re as i ng w h en Q = 10 . F 9. For an iter ate d i nte gra l, one can al way s s wit ch the ord er of int egr ati on. (Sol) 10. The wait ing tune in hour s fo r stu dent s in Cal culu s t ea ch e r' s o 伍c e i s an e xpone ntia lly c te d T an d om v a ri ab l e X w it h a ss oc i at ed pr ob a bi li t y densityfunctioYf()r-面 而 e-丽 .thentheaveragewaitingtimeis10000 h ours . (Sol) If a continuous random va riab le X is e xpon enti ally dis trib uted with the probability density function f(x) = ke— 缸 (0兰 x < oo) . then the expected value E (X) is equal to llk. (下 頁還有試題) 3 填 充 題 Short answer questions (40 points), 每 題 5分 。 ( 不 需詳 列 過 程 ,僅將答 案依題號順序 依序寫在答案 卷第一頁上即可 。) 1.Let R be a region bounded by 0三 z兰 l,0≤ y≤ 1 Then xyeT2dA = - .t e I Answe r : - 戽 (Sol) 1i J { 'x A e‘ t'd,d3 = l-l {j [IJ xe dX] dl = l' d[兰 l' e, dul dg e-i .芒 I:二 e芋\ = 15 ̄[e-i)d J = -.-2 4 2. Let f (x) = k . xye -(r 2+Y 2) be a j oin t p roba bil ity de nsi ty fun cti on o n D = {0 < x < oo,0 < y < oo}, then le Answer: 斗 . - cs 。l ’卡 5 :j :化 各电‘ 卉“》 仪d 子 = l -( (:仅e' z" y- )( 5:芯{9 dg ) 二 幸(兰 f '1 :) (圭亡 ’I :、 : 芸I 。 —,、 c 。 —、,=姜=1 争 阜二斗 )e a n or ma l ra a. b le w it h me an 1 00 a nd v ar i an c e 4 0 0 .I f i t i s given that P(Z < 1.25) = 0.8944, then P(X < 75) = Answer : 0, / o厂 占 . ‘ s。 : ’ P f欠 +呷 , , 二 P c霉 t尘 -’ , =P c罢 : 宅 }, 二 P[暑 (一 I、 2亨 ) 二 P[星 >“ ) 多 ) = / -0, 占 ? 毕 中 : 。1 /0 多b (下頁還有試題) 4 4. Use ELder's method with n = 4 to obtain an approximation of the initial value problem y' = 1十 2xy,y(0) = 0 at x = 1. Round the answers to the nearest hundredth. Answer : y(l)≈ |、≤。 (Sol)告 = 1 + 2xy , Exact solution is: { 2LJn erf(x)ex'} The exact solution is y = gJ; erf(x)eX2 = 21(寺 只 e_r2dt)eX2 = (joe_t2dt)eX2 Indeed, 尝 =吾 ([o e_'2dt)eX2 = e_X2eX2十 (£ o e_t2dt)2xeT2 = 1十 2xy and y(0) = ([o e叫 2dt)eX2lX=o = 0. The exact value of y(l) is y(l) =00 e_"dt)eX2I肛 , = 2. 030 1 W e no w ap p ro xi ma te t he v a l ue o f t h e s o l u t i o n y a t x = 1 b y Eu l e r ' s m et h o d h = '4 0 = 0 .2 5, F (x ,y ) = 1+ 2x y xo = O ,x i = 0 .2 5, x2 = 0 .5 ,X 3 = 0. 75 , X4 = 1 Y o =0 Yi = Yo十 hF(xo,yo) = 0 + 0.25(1十 2 x o x 0) = 0.25 Y2 = Yi十 hF(xi,yi) = 0.25十 0.25(1十 2 x 0.25 x 0.25) = 0.53 y3 = Y2十 hF(x2,Y2) = 0. 53十 0.25(1 + 2 x 0.5 x 0.53) = 0. 91 y4 = y3十 hF(X3,y3) = 0.91 + 0.25(1 + 2 x 0.75 x 0.91) = 1. 50 Wel l, as y ou c an s ee t he a pp r o x i m a t io n i s t ol e r a b l e (下頁還有試題) 5 5. Suppose that x measures the time ( in hou rs) it ta kes fo r a stu den t t o c omp let e an exam. All students are done within two hours and the probability density function for x is f ( x) =譬 if 0 < x < 2. Wh at is the av erag e t une fo r s tud ent s to complete the exam? Answer'圣 二h二 (Sol) E㈤ =6 xf(x)dx=/: x譬 dx=÷hr 6. As you know, when a course ends, students start to forget the material they have learned. One model assumes that the rate at which a student forgets material is proportional to the differenc e b etw een th e m ate ria l cu rre ntl y r e- membered and some positive constant, a. Let y = f (t) b e t he frac tio n o f t he original material remembered t weeks after the course has ended. Set up a . differential equ atio n f or y, usi ng k a s a ny c ons tan t o f p rop ort ion alit y y ou may need (let k > 0) Your equati on wil l c ont ain two co nst ant s; the co nsta nt A(a lso positive) is l n y for all t. A_nswer iis ̄_t_ _' ̄C d-辟, 。卞 . o,吣, fYq勾 =To ̄ (Sol) Let Q(t) denote the amount of material remembered t weeks after the course has ended. Then 7Q = -k(Q - a), k > 0, where a represents the material which will never be dt forgotten. Write y(t) = 9《o) = the frac tion of the orig inal mate rial rem embe red t we eks a fter the course has ended. D ivid i ng t hr ou gh t he e qu at io n鲁 = -k(Q - a ) by Q ( O) , we h av e 詈= —尼殄 —爿),尼>o ,w he re A= a ( 下頁 還有試題) 6 7. While taking a walk along the road where you live , y ou acc iden taL ly dro p y our glove, but you don't know where. The probability density function f(x) for having dropped the glove x kilometers from home (along the road) is f (x) = 2e-2' for x > 0 . W hat is th e pr oba bil ity th at you dr oppe d i t w ith in 1 kilometer of home? Answer: \-e-z (Sol) P(O三X兰 1) =/: 2e-2xdx = 1 - e-2  ̄ 0.864 66 8. Suppose that Congress enacts(國 會 制 定 ) a one-time-only 10% tax rebate(折 扣 ) that is expected to infuse(注 A) ¥y billion, 5 < y < 7 , into the econ- omy. If every person and every corporation is expected t o s pend a pro por tio n x, 0.6 < x < 0.8, of each doll ar rec eiv ed, the n, by the mu lti pli er p rin cip le in economics, the total amount o f s pen dmg S ( 血 b ilj ion s o f d oll ars) ge ner ate d b y this tax rebate is given by S(x,y) =丁兰 百 What is the a ver age to tal am oun t . of spending for the indicated rana'es of the values of x and y? Answer:  ̄O又yl 2 (Sol) The a ver ag e va lue o fc on R =< (x ,y) :o .6 <x <0. 8, 5三夕兰7> is 丽赤而堪只击办出二20. 794 b illion. = 20_QY ) 2 (=-30卫h圭) (下 頁還有試題) 7 計 算 問 答 證 明 題 Please show all your work (60 points), 每 題 10分 , 請 依 題 號 順 序 依 序 寫 在 答案 卷 上 , 可 以 用 中 文或 英 文 作 答 。 請 詳列 計 算 過 程 , 否 則不予計 分。需 標 明 題 號 但 不必 抄 題 。 2 4 1. (10 points) Evaluate xey2 dyd:r: (Sol) / : / : : xey:dydx=/ / xxey2 dA,whereR is the region 月 ={( x, 少 ) : x2三 y≤ 4, o三 x三 2} =<(x, y): O<x<fl, o三 y至 4> Consequently,/ : 丘 42 xeY2dydx = (o/ ; yxeY2dxdy =/ : (孚 ey2)1三 fydy = : 2 eY2dy =÷ ey2矚 = 41eI6 -÷ . ( 下頁還有試題) 8 2. (10 points) The resale value of a ce rta in mac hin e de cre ase s a t a ra te pro port ion al to the machine's current value. The machine was purchased at ¥50,000 and 2 yr later was worth ¥32,000. a. Find an expression for the resale value of the machine at any time t. b. Find the value of the machine after 5 yr. (Sol) 鲁 = -kA, A(O)=500 00, A(2)=32 000, k>o Th e so lut io n is A( t) =C e-k t. A( O) =5 000 0劃C= 50 000 32 0 00 = A ( 2) = 5 0 00 0 e - 2k = ;e - 2 k= 立呈业旦- 上旦 50 000 15 ;尼=专(h 16 - ln2 5) =I n5 - Ln 4 a. A( t) =5 000 0e -( h5- ln 4) t b. A(5)=50000e-On5 ̄4)x5=50000em(4)-5 = 5000045= 50000 x酱等=16384 dolla rs. (下 頁還有試題) 9 3. (10 points) The popul ati on dens ity of a cer tai n c ity is giv en by the fu nct ion /(z,g)= so: OOOl xyl 十20)(y 2+36 ) where the origin (0, 0) gives the location of the go ver nme nt cen ter. Fi nd the po p- ulation inside the rectangular area described loy R = {(x,y)l - 15 < x < 15; -20 < y < 20} :五, 艾艾 S-e,oooK爸 (2l+lo)[旨 ‘+j; ) U 20 争 =4( 知 ooo) - 1 。 蹿 , ‘ j 如 Ⅵ = 200000. 。 锣l十;占 舷% 旷 。 云 √苫J r /:夕 硅乎乎 1C 咒‘斗" :枷。 。。. 陪纠9、;;I川I兰厶I Yl+2。l 200000 吹x 1 l习 奴 穆 ‘ —人 ; 占 ) .(及 a华f -从l。): 4 =掣帆筹)(人祟)一‘。‘。弘等),F l争) /;C 乏 3/ l辞, f ( 下賈 選有試題一 4. (10 points) The scores on an economics examination are normal ly出stri but ed wit h a mean of 72 and a sta nda rd d evi ati on of 16. If th e in str uct or ass ign s a gr ade of A to top lOVo of the class, what is the ap pro xim ate low est sc ore a stu den t ma y h ave and still 1.28 1 ::2 .x obtain an A? (了 乔e- 2 dx≈ 0.4) (Sol) T ̄ 巨髟: 72乱彳 磁谢 Kag/=2夕 吕. Jpr i#e必 w钥才 子 ‘‘uX.t、”。、fIh-岔 猙d。群, /.e. 于( 丫 三 义)‘。, l BcJ广 尸(X;i: 9‘、,P( 父 : 2: i, >三 主 三 1 /s 一 /占 / P(孑2 竽夕 : ~ 厄嗵 罢手品似氏s如棚菇√儿 ’b。吠 4《勿 4, : J斩 芹J, 、 , 争 乙 拿 二 +l-9 / ‘ 弓咒;72+,占C,.1矿)‘尹‘,华}, 口 /,2d 5。+露弘才删詹泊六.c厶好+J9; s 奴Je df,”“d才  ̄d;}√:I'hf} 户,伞护. (下 買遺有 試题) 11 5. (10 points) T he l ife sp an (in ye ars ) o f a cer tai n m ake of ca r b atte ry is an exp one n- tia lly di str ibu ted ran dom va ria ble wi th an e xpe cte d v alu e o f 5 . F ind the pr oba bil ity that the life span of a battery is a. more than 6 yr. b. between 2 and 4 yr. (Sol) f (x ) = ke -h (0 兰 x < 0 0) f (x ) = 0. 2e -0 . 2x a. P( X > 6) = '0 . 2e -0 .2 xd x = li mb + (_ e- 0. 2 ', 1盞 6 = lj IU b_ m( _e -0 2b 十 e -1 2 ) = e- 1. 2 = 0 . 30 1 19 b. P( 2 < X < 4 ) = j2 0 . 2 e - 0. 2 Y d x = (_ e - 0 ; 2 x ,1 爱 = ( e- 0 4 _ e - 0. 8 ) = 0 .2 2 0 9 9 (下 頁還有試題) 12 6. (10 points) A container that has a constant cross section A is皿 ed wit h w ater to height H. The wat er js dis cha rge d th rou gh an ope nin g o f c ross se cti on B a t t he bas e of th e c ont aine r. By usi ng Tor ric ell i's Law , i t c an be sho wn that th e h eig ht h o f t he water at time t satisfies the initial-value problem (1 ft = 12 in ) d九 B一 面 =一 百 √ : 而 危 (o)=H a. Find an expression for h. b. Find the time T it takes for the tank to empty. c. Find T if A=4(ft2), B=l(jn.2), H = 1 6(f t), an d g =32 (ft /sec 2). (Sol) 渤今汐左二‘ / *亙星 =_ tTB历砭 (A’  ̄le4 +,(e白 。J ,s _eA7t7 ̄, 弓云 d 茫 一和万 转 守‘ 2 厉 二普沔 手+ 乙. 5h睫 散 。 , 二 ㈠ 弓 2 河,。‘ f -c- .、 ,书, I 兰I —氟 可士+ 2 \ f fi - J J =卜芽居 廾历/‘ . 、, ,O 二/- 芋 压T 十 同; ; y二 矗 序 d q — 丛生 丛 3 d} 刚 I符 二 , : : q守 l ffl, L, ; j'ft -{万 共 : ’ T二 士 ・ 胆 二 聊 肛 二 批 喲 J4牛 ~ (試 題結束 1
© Copyright 2026 Paperzz