Solved: Evaluating F dot dr Integral for P = pi

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Homework Help Overview

The problem involves evaluating the line integral \(\int F \cdot dr\) where \(F\) is a vector field defined in terms of \(x\) and \(y\), and \(r(t)\) describes a curve parameterized by \(t\). The specific case is set with \(P = \pi\).

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning, Assumption checking

Approaches and Questions Raised

  • Participants discuss the initial steps of dotting the vector field with the differential element and express concerns about the complexity of the resulting expression. There are suggestions to substitute the parameterization into the expression before integration. Others propose considering the curl of the vector field and applying Green's theorem as an alternative approach.

Discussion Status

The discussion is ongoing, with participants exploring different methods to approach the integral. Some guidance has been offered regarding the use of Green's theorem and the evaluation of the curl, but no consensus has been reached on the best path forward.

Contextual Notes

Participants note the need to replace variables based on the parameterization of the curve, and there is an emphasis on simplifying the expression before integration. The discussion reflects a mix of interpretations regarding the application of vector calculus theorems.

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Homework Statement



P = pi

Evaluate [tex]\int[/tex] F [tex]\cdot[/tex]dr where c is the curve given by r(t) = (t+sin[tex]\pi[/tex]t)i + (2tcos[tex]\pi[/tex]t)j

F = (4x3y2 - 2xy3) i + (2x4y - 3x2y2 + 4y3)j



Homework Equations





The Attempt at a Solution



When I dot them I get an extremely long expression.

[tex]\int[/tex] 4x3y2t - 4xy3t - 2xy3sinPt + 4x4yt + 2x4cosPt - 6x2y2t - 3x2y2cosPt + 8y3t + 4y3cosPt dt evaluated from t = 0 to to = 1


2x3y2 - 2xy3 +2Pxy3cosPt + 2x4y + 2Px4ysinPt - 3x2y2 - 3Px2y2sinPt + 4y3 + 4Py3sinPt
 
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I haven'T checked it you have doted correctly but once that is done, you have to replace all the x in there by t+sin(pi*t) and all the y by 2tcos(pi*t). Then simplify if possible and integrate...
 
joemama69 said:
F = (4x3y2 - 2xy3) i + (2x4y - 3x2y2 + 4y3)j

Don't even think of doing it directly!

What is the curl of F? Once you spot that, use Green's theorem or some other property to get the result in one line.
 
Ah hah, Is this right

[tex]\int[/tex]F dot dr = [tex]\int[/tex]curl F dot dA = 0

Because

F = (4x3y2 - 2xy3) i + (2x4y - 3x2y2 + 4y3)j


curl F = (8x3y - 6xy2 - 8x3y + 6xy2)k = 0
 

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