Chapter 6: Applications of Double Integration
Section 6.2: Volume
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Example 6.2.2
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If and is the finite region bounded by the graphs of and , calculate the volume of the region bounded above by the surface and below by the plane .
See Example 6.1.2.
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Solution
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Mathematical Solution
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>
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use plots in
module()
local p1,p2,p3;
p1:=shadebetween(-sqrt(x),sqrt(x),x=0..1,color=red,changefill=[color=blue,transparency=.7],thickness=3):
p2:=shadebetween(-sqrt(x),3-2*x,x=1..9/4,color=black,changefill=[color=green,transparency=.7],thickness=3):
p3:=display(p1,p2,labels=[x,y],tickmarks=[3,[-1.5,-1,0,1]]);
print(p3);
end module:
end use:
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Figure 6.2.2(a) The region R
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Figure 6.2.2(b) The volume to be computed
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The region whose volume is to be computed is shown in Figure 6.2.2(b). The simplest iteration of the double integral that gives the required volume takes the integrand as and uses the order :
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If the order of integration is taken as , then, according to Figure 6.2.2(a), the iterated integral is more difficult:
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Maple Solution - Interactive
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Initialize
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Tools≻Load Package: Student Multivariate Calculus
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Loading Student:-MultivariateCalculus
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Context Panel: Assign Name
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Context Panel: Assign Name
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Context Panel: Assign Name
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Obtain the intersections of the curves bounding
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Write a sequence of the two equations defining the bounding curves.
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Context Panel: Solve≻Solve
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Access the MultiInt command via the Context Panel
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Write , the name of the integrand.
Context Panel: Evaluate and Display Inline
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Context Panel: Student Multivariate Calculus≻Integrate≻Iterated
Fill in both panes (see Figures 5.3.(1, 2)) and select "integral" for the Output
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Context Panel: Evaluate Integral
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Iterate in the order via the template in the Calculus palette
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Calculus palette: Iterated double-integral template
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Context Panel: Evaluate and Display Inline
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Iterate in the order via the template in the Calculus palette
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Calculus palette: Iterated double-integral template
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Context Panel: Evaluate and Display Inline
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The task template in Table 6.2.2(a) iterates in the order . The right-pointing arrow in the left-hand graph indicates that the inner (first) integration is in the -direction. The right-hand image contains a graph of the volume computed by the integral. Since the height of the region in the graph is the constant 1, the volume and the area are the same number.
Tools≻Tasks≻Browse:
Calculus - Multivariate≻Integration≻Visualizing Regions of Integration≻Cartesian 2-D
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Evaluate and Graph
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Area Element
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Value of Integral
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Table 6.2.2(a) Iteration in the order via visualization task-template
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Maple Solution - Coded
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Initialize
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Install the Student MultivariateCalculus package.
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Define the integrand .
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Top-level, using the Int and int commands
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Use the MultiInt command from the Student MultivariateCalculus package
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Use the MultiInt command with a pre-defined domain option
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