This document is posted to help you gain knowledge. Please leave a comment to let me know what you think about it! Share it to your friends and learn new things together.
Poзtomu, izmeniv pordok integrirovani, my moжem zapisatь dvo-no integral po oblasti D v vide odnogo povtornogo integrala:
1∫
0
dy
√4y−y2
∫
−√
4−y2
f(x, y)dx.
Primer 2. Vyqislitь dvono integral∫
D
∫
(54x2y2 + 150x4y4)dxdy
po oblasti D : x = 1, y = x3, y = −√x (ris. 2).
Ris.2
Vybira pordok integrirovani sle-duwim obrazom: vnutrenni integral– po peremenno y, vnexni – po peremen-no x, poluqim
∫
D
∫
(54x2y2 + 150x4y4)dxdy =
1∫
0
dx
x3
∫
−√x
(54x2y2 + 150x4y4)dy ==
1∫
0
dx(
18x2y3 + 30x4y5)∣
∣
∣
x3
−√x
= 11.
6
Primer 3. Vyqislitь plowadь figury D :
x2 + y2 = 12,
y2 =√
6x.
Kak izvestno, plowadь plosko figury D daets dvonym integra-lom S =
∫
D
∫
dxdy. V naxem sluqae oblastь D ograniqena okruжnostь
x2 + y2 = 12 i parabolo y2 =√
6x, kotorye peresekats v toqkahA(
√6,√
6) i B(√
6,−√
6). Koordinaty toqek vlts rexenimi si-
stemy uravneni
x2 + y2 = 12,
y2 =√
6x.Uqityva simmetriqnostь oblasti D (ris. 3)
otnositelьno osi Ox, moжno vyqislitь integralpo polovine oblasti i rezulьtat umnoжitь na 2:
S = 2
∫
D1
∫
dxdy = 2
√6
∫
0
dy
√12−y2
∫
y2/√
6
dx =
Ris. 3
√6
−√
6
= 2
√6
∫
0
dy(
√
12 − y2 − y2
√6
)
= 3π + 2.
Primer 4. Vyqislitь plowadь figury D, gde oblastь zadana sle-
duwim obrazom:
x2 + y2 − 4y = 0,x2 + y2 − 8y = 0,
y =√
3x, x = 0.Figura D ograniqena dvum okruжnostmi
x2 + (y − 2)2 = 4 i x2 + (y − 4)2 = 16 radiusami2 i 4 sootvetstvenno, a takжe dvum prmymiy =
√3x i x = 0 (ris.4). Peredem k polrnym
koordinatam
x = r cos ϕ,y = r sinϕ, (x2 + y2 = r2). Ris. 4
ϕ
Pri зtom oblastь D otobrazits v oblastь G :
r = 4 sinϕ,r = 8 sinϕ,
tg ϕ = 1/√
3, cos ϕ = 0
7
ili G :
r = 4 sinϕ,r = 8 sinϕ,ϕ = π/6, ϕ = π/2
, a зlement plowadi dxdy =⇒ rdrdϕ.
Poзtomu
S =
∫
D
∫
dxdy =
∫
G
∫
rdrdϕ =
π/2∫
π/6
dϕ
8 sin ϕ∫
4 sin ϕ
rdr = 24
π/2∫
π/6
sin2 ϕdϕ = 4π + 3√
3.
Primer 5. Vyqislitь plowadь figury D : (x2 + y2)2 = a2(x2 − 3y2).Preжde vsego otmetim, qto x2 − 3y2 ≥ 0, tak kak neotricatelьna le-va qastь ravenstva, a sama figura simmetriqna otnositelьno oseOx i Oy. Peredem k polrnym koordinatam, pri зtom poluqim
naxem sluqae dl k sleduet ostavitь znaqeni k = 0 i k = 1. Takim
obrazom, oblastь D =⇒ G :
r = a√
2 cos 2ϕ − 1 ,−π/6 ≤ ϕ ≤ π/6, 5/6π ≤ ϕ ≤ 7/6π.
Dalee integriruem po qetverto qasti oblasti G i poluqennyrezulьtat umnoжaem na 4:
S = 4
π/6∫
0
dϕ
a√
2 cos 2ϕ−1∫
0
rdr = 2a2
π/6∫
0
(2 cos 2ϕ − 1)dϕ = a2(√
3 − π
2
)
.
Primer 6. Vyqislitь trono integral
∫∫
Ω
∫
x2z dxdydz po oblasti
Ω :
y = 3x, y = 0, x = 2,z = xy, z = 0.
Ishodny integral zapixem v vide
∫∫
Ω
∫
x2z dxdydz =
∫
D
∫
dxdy
xz∫
0
x2z dz ,
8
gde oblastь D – proekci tela Ω na plos-kostь xOy, t. e. D : y = 3x, y = 0, x = 2 (ris. 5).Dalьnexie vyqisleni dostatoqno prosty:
∫
D
∫
dxdy
xz∫
0
x2z dz =
∫
D
∫
dxdy x2 z2
2
∣
∣
∣
∣
xy
0
=
=1
2
2∫
0
x4 dx
3x∫
0
y2 dy = 144
.
Ris.5
Primer 7. Vyqislitь obъem tela Ω :
x = 17√
2y, x = 2√
2y,z = 0, z + y = 1/2.
Telo Ω ograniqeno cilindriqeskimi poverh-nostmi x = 17
√2y i x = 17
√2y i ploskostmi
z = 0 i z + y = 1/2 (otmetim, qto x ≥ 0). Egoproekci na xOy predstavlet sobo oblastьD : x = 17
√2y, x = 2
√2y, y = 1/2 (ris. 6). Poзtomu
V =
∫∫
Ω
∫
dxdydz =
∫
D
∫
dxdy
1/2−y∫
0
dz =
∫
D
∫(
1
2− y
)
dxdy =
1/2∫
0
(
1
2− y
)
dy
17√
2y∫
2√
2y
dx = 1 .
Ris.6
Primer 8. Vyqislitь obъem tela Ω :
x2 + y2 + 2x = 0,
z =25
4− y2, z = 0.
Dannoe telo predstavlet sobo cilindr, uravnenie kotorogomoжno zapisatь v vide (x + 1)2 + y2 = 1, ograniqenny snizu plos-kostь xOy, a sverhu cilindriqesko poverhnostь s obrazuwe,parallelьno osi Ox. Lboe seqenie зto poverhnosti ploskostь,perpendikulrno osi Ox, vlets parabolo z = 25/4 − y2. Obъemtela raven:
9
V =
∫∫
Ω
∫
dxdydz =
∫
D
∫
dxdy
25/4−y2
∫
0
dz =
∫
D
∫(
25
4− y2
)
dxdy,
gde oblastь D predstavlet sobo krug (x + 1)2 + y2 ≤ 1, s centrom vtoqke C(−1, 0) i radiusom 1 (ris. 7).
Vyqisl dvono integral, peredem kpolrnym koordinatam, pri зtom oblastь Dotobrazits v G : r = −2 cos ϕ, π/2 ≤ ϕ ≤ 3π/2.Vvidu simmetrii zadaqi integrirovatь moж-no po polovine oblasti i rezulьtat udvoitь.
Takim obrazom,
V = 2
∫
G1
∫(
25
4− y2
)
dϕ rdr = 2
π∫
π/2
dϕ
−2 cos ϕ∫
0
rdr =
ϕ
Ris.7
=
π∫
π/2
cos2 ϕ (25−8 sin2 ϕ cos2 ϕ) dϕ =1
2
π∫
π/2
(1+cos 2ϕ)(25−2 sin2 2ϕ) dϕ = 6π .
Zameqanie. V зto zadaqe moжno bylo srazu pereti k cilindri-qeskim koordinatam: x = r cos ϕ, y = r sinϕ, z = z. Togda
nahodwus nad ploskostь xOy, na-krytu sverhu sferiqesko poverhno-stь x2 + y2 + z2 = 36 s centrom v naqa-le koordinat i radiusom 6 (ris. 8.) Takkak ono obladaet cilindriqesko simme-trie (osь Oz vlets osь simmetriibeskoneqnogo pordka), udobno srazu жepereti k cilindriqeskim koordinatam:
x = r cos ϕ,y = r sinϕ,z = z;
3√
3
Ris.8
Ω =⇒ Λ :
z = +√
36 − r2,
z =r√3;
dxdydz =⇒ dϕ rdrdz.
Poluqim:
V =
∫∫
Λ
∫
dϕ rdrdz =
∫
D
∫
dϕ rdr
√36−r2∫
r/√
3
dz =
∫
D
∫(
√
36 − r2 − r√3
)
dϕ rdr.
Oblastь D :
r = 3√
3,0 ≤ ϕ ≤ 2π
estь proekci Ω na ploskostь xOy i
predstavlet sobo krug s centrom v naqale koordinat, radius koto-
rogo r = 3√
3 vlets rexeniem sistemy uravneni
z =√
36 − r2,
z =r√3;
V =
∫
D
∫(
√
36 − r2 − r√3
)
dϕ rdr
2π∫
0
dϕ
3√
3∫
0
(
√
36 − r2 − r√3
)
rdr = 72π.
Primer 10. Vyqislitь obъem tela Ω :
36 ≤ x2 + y2 + z2 ≤ 144,
−√
x2 + y2
3≤ z ≤ −
√
x2 + y2
15,
0 ≤ y ≤ −√
3x.
11
Naxe telo zaklqeno meжdu koniqeskimi x2+y2 = 3z2 i x2 + y2 = 15z2
i koncentriqeskimi sferiqeskimi x2 + y2 + z2 = 36 i x2 + y2 + z2 = 144poverhnostmi i rassekaets ploskostmi y = 0 i y = −
√3x. Raspolo-
жeno ono pod ploskostь xOy (z ≤ 0). Seqeni tela koordinatnymiploskostmi xOz i xOy pokazany na ris. 9 i 10.
Ris. 9
θ
z=−|x|/√
15
z=−|x|/√
3
Ris. 10
ϕy=−
√3x
Peredem k sferiqeskim koordinatam po formulam:
x = r sin θ cos ϕ,y = r sin θ sinϕ,z = r cos θ;
dxdydz =⇒ dϕ sin θdθ r2dr.
Iz uslovi zadaqi (i risunkov) vidno, qto x ≤ 0 i z ≤ 0, a зtooznaqaet, qto cos ϕ ≤ 0 i cos θ ≤ 0, pri зtom sin θ ≥ 0, tak kak ugolθ ∈ [0, π]. Poзtomu oblastь Ω otobraжaets v Λ:
Λ :
36 ≤ r2 ≤ 144,
−√
r2 sin2 θ
3≤ r cos θ ≤ −
√
r2 sin2 θ
15,
0 ≤ r sin θ sinϕ ≤ −r√
3 sin θ cos ϕ
⇒
6 ≤ r ≤ 12,
−sin θ√3
≤ cos θ ≤ −sin θ√15
,
0 ≤ sinϕ ≤ −√
3 cos ϕ
Rassmotrim podrobnee neravenstvo 0 ≤ sinϕ ≤ −√
3 cos ϕ. Takkak cos ϕ ≤ 0, to dl ego rexeni udobno vvesti novu peremennuϕ = π − ϕ, togda ϕ = π − ϕ. Pri зtom sinϕ = sin(π − ϕ) = sin ϕ, acos ϕ = cos(π − ϕ) = − cos ϕ (cos ϕ ≥ 0). Razdeliv neravenstvo nacos ϕ, poluqim 0 ≤ tg ϕ ≤
√3. Iz mnoжestva ego rexeni vybira-
em 0 ≤ ϕ ≤ π/3 ili, vernuvxisь k peremenno ϕ, 2π/3 ≤ ϕ ≤ π(sm. ris. 10). Podobnym obrazom iz neravenstva, soderжawego ugol θ,poluqim π − arctg
√15 ≤ θ ≤ 2π/3. Teperь oblastь Λ zapixem v okon-
12
qatelьnom vide:
Λ :
6 ≤ r ≤ 12,
π − arctg√
15 ≤ θ ≤ 2π
3,
2π
3≤ ϕ ≤ π.
Obъem vyqislets prosto:
V =
∫∫
Λ
∫
dϕ sin θdθ r2dr =
π∫
2π/3
dϕ
2π/3∫
π−arctg√
15
sin θdθ
12∫
6
r2dr =
= 168π
(
1
2− cos(arctg
√15)
)
.
Preobrazuem rezulьtat, ispolьzu formulu cos α = 1/√
1 + tg2 α :
cos(arctg√
15) =1
√
1 + tg2(arctg√
15)=
1
4.
Okonqatelьno imeem: V = 42π.
13
Rasqetnye zadani
1. Izmenitь pordok integrirovani
V zadaqah 1.1–1.30 izmenitь pordok integrirovani v zadannyhpovtornyh integralah. Oblastь integrirovani izobrazitь na qer-teжe.
1.1.
−1∫
−2
dy
0∫
−√2+y
f(x, y) dx +
0∫
−1
dy
0∫
−√−y
f(x, y) dx .
1.2.
1∫
0
dy
0∫
−√y
f(x, y) dx +
√2
∫
1
dy
0∫
−√
2−y2
f(x, y) dx .
1.3.
1∫
0
dy
y∫
0
f(x, y) dx +
√2
∫
1
dy
√2−y2
∫
0
f(x, y) dx .
1.4.
1∫
0
dy
√y
∫
0
f(x, y) dx +
2∫
1
dy
√2−y
∫
0
f(x, y) dx .
1.5.
−1∫
−√
2
dx
0∫
−√
2−x2
f(x, y) dy +
0∫
−1
dx
0∫
x
f(x, y) dy .
1.6.
1/√
2∫
0
dy
arcsin y∫
0
f(x, y) dx +
1∫
1/√
2
dy
arccos y∫
0
f(x, y) dx .
1.7.
−1∫
−2
dy
√2+y
∫
0
f(x, y) dx +
0∫
−1
dy
√−y∫
0
f(x, y) dx .
14
1.8.
1∫
0
dy
0∫
−√y
f(x, y) dx +
e∫
1
dy
− ln y∫
−1
f(x, y) dx .
1.9.
−1∫
−√
2
dx
√2−x2∫
0
f(x, y) dy +
0∫
−1
dx
x2
∫
0
f(x, y) dy .
1.10.
−√
3∫
−2
dx
0∫
−√
4−x2
f(x, y) dy +
0∫
−√
3
dx
0∫
−2+√
4−x2
f(x, y) dy .
1.11.
1∫
0
dx
1∫
1−x2
f(x, y) dy +
e∫
1
dx
1∫
lnx
f(x, y) dy .
1.12.
1∫
0
dy
3√
y∫
0
f(x, y) dx +
2∫
1
dy
2−y∫
0
f(x, y) dx .
1.13.
π/4∫
0
dy
sin y∫
0
f(x, y) dx +
π/2∫
π/4
dy
cos y∫
0
f(x, y) dx .
1.14.
−1∫
−2
dx
0∫
−(2+x)
f(x, y) dy +
0∫
−1
dx
0∫
3√
x
f(x, y) dy .
1.15.
1∫
0
dy
√y
∫
0
f(x, y) dx +
e∫
1
dy
1∫
ln y
f(x, y) dx .
1.16.
1∫
0
dy
0∫
−√y
f(x, y) dx +
2∫
1
dy
0∫
−√2−y
f(x, y) dx .
1.17.
1∫
0
dy
0∫
−y
f(x, y) dx +
√2
∫
1
dy
0∫
−√
2−y2
f(x, y) dx .
15
1.18.
1∫
0
dy
y3
∫
0
f(x, y) dx +
2∫
1
dy
2−y∫
0
f(x, y) dx .
1.19.
√3
∫
0
dx
0∫
−2+√
4−x2
f(x, y) dy +
2∫
√3
dx
0∫
−√
4−x2
f(x, y) dy .
1.20.
−1∫
−2
dy
0∫
−(2+y3)
f(x, y) dx +
0∫
−1
dy
0∫
3√
y
f(x, y) dx .
1.21.
1∫
0
dy
y∫
0
f(x, y) dx +
e∫
1
dy
1∫
ln y
f(x, y) dx .
1.22.
1∫
0
dx
x2
∫
0
f(x, y) dy +
√2
∫
1
dx
√2−x2∫
0
f(x, y) dy .
1.23.
π/4∫
0
dx
sin x∫
0
f(x, y) dy +
π/2∫
π/4
dx
cos x∫
0
f(x, y) dy .
1.24.
−1∫
−√
2
dy
0∫
−√
2−y2
f(x, y) dx +
0∫
−1
dy
0∫
y
f(x, y) dx .
1.25.
1∫
0
dx
x3
∫
0
f(x, y) dy +
2∫
1
dx
2−x∫
0
f(x, y) dy .
1.26.
√3
∫
0
dx
2−√
4−x2∫
0
f(x, y) dy +
2∫
√3
dx
√4−x2∫
0
f(x, y) dy .
1.27.
1∫
0
dx
0∫
−√x
f(x, y) dy +
2∫
1
dx
0∫
−√
2−x
f(x, y) dy .
16
1.28.
1∫
0
dx
x∫
0
f(x, y) dy +
√2
∫
1
dx
√2−x2∫
0
f(x, y) dy .
1.29.
1∫
0
dy
√y
∫
0
f(x, y) dx +
√2
∫
1
dy
√2−y2
∫
0
f(x, y) dx .
1.30.
1∫
0
dx
√x
∫
0
f(x, y) dy +
2∫
1
dx
√2−x
∫
0
f(x, y) dy .
2. Vyqislitь dvonye integraly.
V zadaqah 2.1–2.30 vyqislitь dvonye integraly∫
D
∫
f(x, y) dxdy,
esli oblastь D zadana ukazannymi linimi.
2.1.
∫
D
∫
(12x2y2+16x3y3) dxdy,
D : x = 1, y = x2, y = −√x .
2.2.
∫
D
∫
(9x2y2 + 48x3y3) dxdy,
D : x = 1, y =√
x, y = −x2.
2.3.
∫
D
∫
(36x2y2−96x3y3) dxdy,
D : x = 1, y = 3√
x, y = −x3.
2.4.
∫
D
∫
(12x2y2+16x3y3) dxdy,
D : x = 1, y = x3, y = − 3√
x .
2.5.
∫
D
∫
(27x2y2+48x3y3) dxdy,
D : x = 1, y = x2, y = − 3√
x .
2.6.
∫
D
∫
(18x2y2+32x3y3) dxdy,
D : x = 1, y = 3√
x, y = −x2.
2.7.
∫
D
∫
(18x2y2+32x3y3) dxdy,
D : x = 1, y = x3, y = −√x .
2.8.
∫
D
∫
(27x2y2+48x3y3) dxdy,
D : x = 1, y =√
x, y = −x3.
2.9.
∫
D
∫
(4xy + 3x2y2) dxdy,
D : x = 1, y = x2, y = −√x .
2.10.
∫
D
∫
(12xy + 9x2y2) dxdy,
D : x = 1, y =√
x, y = −x2.
2.11.
∫
D
∫
(8xy + 9x2y2) dxdy,
D : x = 1, y = 3√
x, y = −x3.
2.12.
∫
D
∫
(24xy + 18x2y2) dxdy,
D : x = 1, y = x3, y = − 3√
x .
17
2.13.
∫
D
∫
(12xy + 27x2y2) dxdy,
D : x = 1, y = x2, y = − 3√
x .
2.14.
∫
D
∫
(8xy + 18x2y2) dxdy,
D : x = 1, y = 3√
x, y = −x2.
2.15.
∫
D
∫
(4
5xy +
9
11x2y2) dxdy,
D : x = 1, y = x3, y = −√x .
2.16.
∫
D
∫
(4
5xy + 9x2y2) dxdy,
D : x = 1, y =√
x, y = −x3.
2.17.
∫
D
∫
(24xy − 48x3y3) dxdy,
D : x = 1, y = x2, y = −√x .
2.18.
∫
D
∫
(6xy + 24x3y3) dxdy,
D : x = 1, y =√
x, y = −x2.
2.19.
∫
D
∫
(4xy + 16x3y3) dxdy,
D : x = 1, y = 3√
x, y = −x3.
2.20.
∫
D
∫
(4xy + 16x3y3) dxdy,
D : x = 1, y = x3, y = − 3√
x .
2.21.
∫
D
∫
(44xy + 16x3y3) dxdy,
D : x = 1, y = x2, y = − 3√
x .
2.22.
∫
D
∫
(4xy + 176x3y3) dxdy,
D : x = 1, y = 3√
x, y = −x2.
2.23.
∫
D
∫
(xy − 4x3y3) dxdy,
D : x = 1, y = x3, y = −√x .
2.24.
∫
D
∫
(4xy + 176x3y3) dxdy,
D : x = 1, y =√
x, y = −x3.
2.25.
∫
D
∫
(6x2y2 +25
3x4y4) dxdy,
D : x = 1, y = x2, y = −√x .
2.26.
∫
D
∫
(9x2y2+25x4y4) dxdy,
D : x = 1, y =√
x, y = −x2.
2.27.
∫
D
∫
(3x2y2 +50
3x4y4) dxdy,
D : x = 1, y = 3√
x, y = −x3.
2.28.
∫
D
∫
(9x2y2+25x4y4) dxdy,
D : x = 1, y = x3, y = − 3√
x .
2.29.
∫
D
∫
(xy − 9x5y5) dxdy,
D : x = 1, y = 3√
x, y = −x2.
2.30.
∫
D
∫
(54x2y2+150x4y4) dxdy,
D : x = 1, y = x3, y = −√x .
18
3. Vyqislitь plowadь plosko figury (I)
V zadaqah 3.1–3.30 vyqislitь s pomowь dvonogo integrala v de-kartovyh koordinatah plowadь plosko figury, ograniqenno uka-zannymi linimi.
V zadaqah 6.1–6.30 vyqislitь s pomowь tronogo integrala obъ-em tela, ograniqennogo ukazannymi poverhnostmi. Sdelatь qerteжdannogo tela i ego proekcii na ploskostь xOy.
6.1. y = 16√
2x, y =√
2x,z = 0, x + z = 2.
6.2. y = 5√
x, y = 5x/3,z = 0, z = 5
√x/3 + 5.
6.3. x2 + y2 = 2, y =√
x, y = 0,z = 0, z = 15x.
6.4. x + y = 2, y =√
x,z = 12y, z = 0.
6.5. x = 20√
2y, x = 5√
2y,z = 0, z + y = 1/2.
6.6. x = 5√
y/2, x = 5y/6,z = 0, z = 5(3 +
√y)/6.
6.7. x2 + y2 = 2, x =√
y, x = 0,z = 0, z = 30y.
6.8. x + y = 2, x =√
y,z = 12x/5, z = 0.
6.9. y = 17√
2x, y = 2√
2x,z = 0, x + z = 1/2.
6.10. y = 5√
x/3, y = 5x/9,z = 0, z = 5(3 +
√x)/9.
6.11. x2 + y2 = 8, y =√
2x, y = 0,z = 0, z = 15x/11.
6.12. x + y = 4, y =√
2x,z = 0, z = 3y.
6.13. x = 5√
y/6, x = 5y/18,z = 0, z = 5(3 +
√y)/18.
6.14. x = 19√
2y, x = 4√
2y,z + y = 2, z = 0.
6.15. x2 + y2 = 8, x =√
2y, x = 0,z = 0, z = 30y/11.
6.16. x + y = 4, x =√
2y,z = 0, z = 3x/5.
6.17. y = 6√
3x, y =√
3x,z = 0, x + y = 3.
6.18. y = 5√
x/6, y = 5x/18,z = 0, z = 5(3 +
√x)/18.
6.19. x2 +y2 = 18, y =√
3x, y = 0,z = 0, z = 5x/11.
6.20. x + y = 6, y =√
3x,z = 0, z = 4y.
6.21. x = 7√
3y, x = 2√
3y,z = 0, y + z = 3.
6.22. x = 5√
y/3, x = 5y/9,z = 0, z = 5(3 +
√y)/9.
6.23. x2 + y2 = 18, x =√
3y,x = 0, z = 0, z = 10y/11.
6.24. x + y = 6, x =√
3y,z = 4x/5, z = 0.
6.25. y =√
15x, y =√
15x,z = 0, z =
√15(1 +
√x).
6.26. x2 + y2 = 50, y =√
5x,z = 0, z = 3x/11, y = 0.
6.27. x + y = 8, y =√
4x,z = 0, z = 3y.
6.28. x = 16√
2y, x =√
2y,z + y = 2, z = 0.
25
6.29. x = 15√
y, x = 15y,z = 0, z = 15(1 +
√y).
6.30. x2 + y2 = 50, x =√
5y,z = 0, z = 6y/11, x = 0.
7. Vyqislitь obъem tela (II)
V zadaqah 7.1–7.30 vyqislitь s pomowь tronogo integrala obъ-em tela, ograniqennogo ukazannymi poverhnostmi, ispolьzu cilin-driqeskie koordinaty.