Chapter 9: Vector Calculus
Section 9.7: Conservative and Solenoidal Fields
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Example 9.7.6
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For , show that the line integral along any member of the family of curves , , has the value 1.
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Solution
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Mathematical Solution
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The slider in Figure 9.7.6(a) varies the value of over the range , and the curve thereby shown is a member of the given family of curves.
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The astute reader will realize that for , the extended family would not pass through the origin. Indeed, the general position vector would become
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which means that this particular curve would pass through at .
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Writing the members of the family via the position vector
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>
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Explore(plots[:-spacecurve]([t,t^k,t^k],t=0..1,labels=[t,"",""],color=red,thickness=2,labels=[x,y,z],orientation=[-35,80,0],tickmarks=[2,2,2]),':-parameters'=[k=1.0..25.],':-initialvalues'=[k=3.0]);
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Figure 9.7.6(a) The family of curves
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the integral of becomes, after a simplification,
Under the assumption , this integral evaluates to 1.
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Maple Solution - Interactive
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Table 9.7.6(a) provides a solution in which the LineInt command is accessed via the Context Panel.
Initialize
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Tools≻Load Package: Student Vector Calculus
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Loading Student:-VectorCalculus
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Tools≻Tasks≻Browse: Calculus - Vector≻
Vector Algebra and Settings≻
Display Format for Vectors
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Press the Access Settings button and select
"Display as Column Vector"
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Display Format for Vectors
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Define the vector field F
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Enter the components of F in a free vector.
Context Panel: Evaluate and Display Inline
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Context Panel: Student Vector Calculus≻Conversions≻To Vector Field
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Context Panel: Assign to a Name≻F
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Form and evaluate the line integral of F along curves of the family
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Write the name F and press the Enter key.
Context Panel: Student Vector Calculus≻Line Integral
Complete the dialog as per Figure 9.7.6(b)
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Context Panel: Simplify≻Simplify
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Context Panel: Evaluate Integral
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Context Panel: Simplify≻Assuming Real Range
Complete the dialog as per Figure 9.7.6(c).
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Figure 9.7.6(b) Line Integral Domain dialog
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Figure 9.7.6(c) RealRange
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Table 9.7.6(a) Solution via the LineInt command accessed from the Context Panel
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Maple Solution - Coded
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Table 9.7.6(b) provides a solution via the LineInt command.
Initialize
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Install the Student VectorCalculus package.
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Form and evaluate the line integral of F along curves of the family
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Apply the simplify command to the integral returned by the LineInt command.
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Evaluate the line integral under an appropriate assumption on .
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Table 9.7.6(b) Solution via the LineInt command
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