Section 4.7

Methods for Computing Volume

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Problem 2456

Find the volume of a hip roof, whose base is a rectangle with side lengths aa and bb, whose ridge has length cc, and whose height is hh.

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Problem 2457

Find the volume of a truncated wedge whose parallel top and bottom faces are rectangles with side lengths AA, BB and aa, bb respectively, and whose height equals hh.

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Problem 2458

Find the volume of a truncated cone (frustum) whose top and bottom faces are ellipses with semi-axes AA, BB and aa, bb respectively, and whose height equals hh.

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Problem 2459

Find the volume of a paraboloid of revolution whose base is SS and whose height equals HH.

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Problem 2460

Suppose the area S=S(x)S=S(x) of the cross-section of a solid perpendicular to the OxOx axis varies according to the following quadratic law:

S(x)=Ax2+Bx+C(a⩽x⩽b), S(x)=Ax^{2}+Bx+C\quad (a\leqslant x\leqslant b) ,

where AA, BB, and CC are constants.

Prove that the volume of this solid equals

V=H6[S(a)+4S(a+b2)+S(b)], V=\dfrac {H}{6}\left[S(a)+4S\left(\dfrac {a+b}{2}\right)+S(b)\right] ,

where H=b−aH=b-a (Simpson's formula).

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Problem 2461

A solid is the set of points M(x,y,z)M(x,y,z) such that 0⩽z⩽10\leqslant z\leqslant 1, and moreover, if zz is rational, 0⩽x⩽10\leqslant x\leqslant 1, 0⩽y⩽10\leqslant y\leqslant 1; while if zz is irrational, −1⩽x⩽0-1\leqslant x\leqslant 0, −1⩽y⩽0-1\leqslant y\leqslant 0. Prove that although the corresponding integral is

∫01S(z)dz=1, \int _{0}^{1}S(z) dz=1 ,

the volume of this solid does not exist.

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Problem 2462

Find the volume enclosed by the following surfaces:

x2a2+y2b2=1,z=−cax,z=0. \dfrac {x^{2}}{a^{2}}+\dfrac {y^{2}}{b^{2}}=1 ,\quad z=-\dfrac {c}{a}x ,\quad z=0 .
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Problem 2463

Find the volume enclosed by the following surfaces:

x2a2+y2b2+z2c2=1(ellipsoid). \dfrac {x^{2}}{a^{2}}+\dfrac {y^{2}}{b^{2}}+\dfrac {z^{2}}{c^{2}}=1\quad (\text{ellipsoid}) .
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Problem 2464

Find the volume enclosed by the following surfaces:

x2a2+y2b2−z2c2=1,z=±c. \dfrac {x^{2}}{a^{2}}+\dfrac {y^{2}}{b^{2}}-\dfrac {z^{2}}{c^{2}}=1 ,\quad z=\pm c .
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Problem 2465

Find the volume enclosed by the following surfaces:

x2+z2=a2,y2+z2=a2. x^{2}+z^{2}=a^{2} ,\quad y^{2}+z^{2}=a^{2} .
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Problem 2466

Find the volume enclosed by the following surfaces:

x2+y2+z2=a2,x2+y2=ax. x^{2}+y^{2}+z^{2}=a^{2} ,\quad x^{2}+y^{2}=ax .
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Problem 2467

Find the volume enclosed by the following surfaces:

z2=b(a−x),x2+y2=ax. z^{2}=b(a-x) ,\quad x^{2}+y^{2}=ax .
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Problem 2468

Find the volume enclosed by the following surfaces:

x2a2+y2z2=1(0<z<a). \dfrac {x^{2}}{a^{2}}+\dfrac {y^{2}}{z^{2}}=1\quad (0<z<a) .
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Problem 2469

Find the volume enclosed by the following surfaces:

x+y+z2=1,x=0,y=0,z=0. x+y+z^{2}=1 ,\quad x=0 ,\quad y=0 ,\quad z=0 .
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Problem 2470

Find the volume enclosed by the following surface:

x2+y2+z2+xy+yz+zx=a2. x^{2}+y^{2}+z^{2}+xy+yz+zx=a^{2} .
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Problem 2471

Prove that the volume of the solid of revolution obtained by rotating the area

a⩽x⩽b,0⩽y⩽y(x), a\leqslant x\leqslant b ,\quad 0\leqslant y\leqslant y(x) ,

(where y(x)y(x) is a continuous function) about the OyOy axis equals

Vy=2π∫abxy(x)⋅dx. V_{y}=2\pi \int _{a}^{b}xy(x)\cdot dx .
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Problem 2472

Find the volume enclosed by the surface formed by rotating the following curve: y=b(xa)32(0⩽x⩽a)y=b\left(\dfrac {x}{a}\right)^{\frac{3}{2}}(0\leqslant x\leqslant a) about the OxOx axis (semicubical parabola).

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Problem 2473

Find the volume enclosed by the surface formed by rotating the following curve: y=2x−x2y=2x-x^{2}, y=0y=0:

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(a)

about the OxOx axis;

(b)

about the OyOy axis.

Problem 2474

Find the volume enclosed by the surface formed by rotating the following curve: y=sin⁡xy=\sin x, y=0y=0 (0⩽x⩽π0\leqslant x\leqslant \pi):

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(a)

about the OxOx axis;

(b)

about the OyOy axis.

Problem 2475

Find the volume enclosed by the surface formed by rotating the following curve: y=b(xa)2y=b\left(\dfrac {x}{a}\right)^{2}, y=b∣xa∣y=b\left|\dfrac {x}{a}\right|:

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(a)

about the OxOx axis;

(b)

about the OyOy axis.

Problem 2476

Find the volume enclosed by the surface formed by rotating the following curve: y=e−xy=e^{-x}, y=0y=0 (0⩽x<+∞0\leqslant x<+\infty):

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(a)

about the OxOx axis;

(b)

about the OyOy axis.

Problem 2477

Find the volume enclosed by the surface formed by rotating the following curve: x2+(y−b)2=a2x^{2}+(y-b)^{2}=a^{2} (0<a⩽b0<a\leqslant b) about the OxOx axis.

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Problem 2478

Find the volume enclosed by the surface formed by rotating the following curve: x2−xy+y2=a2x^{2}-xy+y^{2}=a^{2} about the OxOx axis.

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Problem 2479

Find the volume enclosed by the surface formed by rotating the following curve: y=e−xsin⁡xy=e^{-x}\sqrt{\sin x} (0⩽x<+∞0\leqslant x<+\infty) about the OxOx axis.

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Problem 2480

Find the volume enclosed by the surface formed by rotating the following curve: x=a(t−sin⁡t)x=a(t-\sin t), y=a(1−cos⁡t)y=a(1-\cos t) (0⩽t⩽2π0\leqslant t\leqslant 2\pi), y=0y=0:

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(a)

about the OxOx axis;

(b)

about the OyOy axis;

(c)

about the line y=2ay=2a.

Problem 2481

Find the volume enclosed by the surface formed by rotating the following curve: x=asin⁡3tx=a\sin^{3}t, y=bcos⁡3ty=b\cos^{3}t (0⩽t⩽2π0\leqslant t\leqslant 2\pi):

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(a)
(b)

about the OyOy axis.

Problem 2481.1

about the OxOx axis;

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(a)
(b)
Problem 2482

Prove that the volume obtained by rotating the area

0⩽α⩽φ⩽β⩽π,0⩽r⩽r(φ) 0\leqslant \alpha \leqslant \varphi \leqslant \beta \leqslant \pi ,\quad 0\leqslant r\leqslant r(\varphi )

(where φ\varphi and rr are polar coordinates) about the polar axis equals

V=2π3∫αβr3(φ)sin⁡φdφ. V=\dfrac {2\pi }{3}\int _{\alpha }^{\beta }r^{3}(\varphi )\sin \varphi d\varphi .
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Problem 2483

Find the volume obtained by rotating the following area given in polar coordinates: r=a(1+cos⁡φ)r=a(1+\cos \varphi ) (0⩽φ⩽2π0\leqslant \varphi \leqslant 2\pi):

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(a)

about the polar axis;

(b)

about the line rcos⁡φ=−a4r\cos \varphi =-\dfrac {a}{4}.

Problem 2484

Find the volume obtained by rotating the following area given in polar coordinates: (x2+y2)2=a2(x2−y2)(x^{2}+y^{2})^{2}=a^{2}(x^{2}-y^{2}):

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(a)
(b)
(c)

about the line y=xy=x.

Problem 2484.1

about the OxOx axis;

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Problem 2484.2

about the OyOy axis;

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Problem 2485

Find the volume of the solid of revolution obtained by rotating about the polar axis the area

a⩽r⩽a2sin⁡2φ a\leqslant r\leqslant a\sqrt{2\sin 2\varphi }
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