Line integral across a vector field

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Homework Help Overview

The discussion revolves around evaluating the line integral of a vector field, specifically \(\int_C \mathbf F\cdot d \mathbf r\) where \(\mathbf F = x^2\vec{i}+e^{\sin^4{y}}\vec{j}\) and \(C\) is defined as the curve segment \(y=x^2\) from the points \((-1,1)\) to \((1,1)\).

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss parametrizing the curve \(C\) and express familiarity with applying the line integral equations and Green's theorem. There is a focus on the challenges posed by the term \(e^{\sin^4{y}}\) during integration.

Discussion Status

Some participants are exploring different approaches to the integral, including checking for path independence and considering alternative paths. There is no explicit consensus on a solution, but the discussion is ongoing with various strategies being considered.

Contextual Notes

Participants note the complexity of integrating the term \(e^{\sin^4{y}}\) and the implications of using Green's theorem, suggesting that there may be a missing insight or trick in the problem setup.

clandarkfire
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Homework Statement


[tex]\int_C \mathbf F\cdot d \mathbf r[/tex] where [tex]\mathbf F = x^2\vec{i}+e^{\sin^4{y}}\vec{j}[/tex]
and C is the segment of y=x^2 from (-1,1) to (1,1).

Homework Equations


[tex]\int_C \mathbf F\cdot d \mathbf r=\int_a^b \mathbf F( \mathbf r(t))\cdot r'(t) dt=\int_C Pdx+Qdy[/tex] where [tex]\mathbf F = P\vec{i}+Q\vec{j}[/tex]

The Attempt at a Solution


I parametrize C:
[tex]\mathbf r(t)=<t,t^2>|-1\leq t \leq 1[/tex]
Well, I know how to apply the equations above as well as Green's theorem (I use this by letting C2 be a line from (1,1) to (-1,1) and integrating across the enclosed disk D), but no matter what I do, I find myself having to integrate some version of [tex]e^{\sin^4{y}}[/tex]
There has to be some trick I'm missing. Could someone point me in the right direction?
 
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clandarkfire said:

Homework Statement


[tex]\int_C \mathbf F\cdot d \mathbf r[/tex] where [tex]\mathbf F = x^2\vec{i}+e^{\sin^4{y}}\vec{j}[/tex]
and C is the segment of y=x^2 from (-1,1) to (1,1).

Homework Equations


[tex]\int_C \mathbf F\cdot d \mathbf r=\int_a^b \mathbf F( \mathbf r(t))\cdot r'(t) dt=\int_C Pdx+Qdy[/tex] where [tex]\mathbf F = P\vec{i}+Q\vec{j}[/tex]

The Attempt at a Solution


I parametrize C:
[tex]\mathbf r(t)=<t,t^2>|-1\leq t \leq 1[/tex]
Well, I know how to apply the equations above as well as Green's theorem (I use this by letting C2 be a line from (1,1) to (-1,1) and integrating across the enclosed disk D), but no matter what I do, I find myself having to integrate some version of [tex]e^{\sin^4{y}}[/tex]
There has to be some trick I'm missing. Could someone point me in the right direction?
If [itex]\displaystyle \mathbf r(t)=<t,\,t^2>\,,\[/itex] then [itex]\displaystyle d\mathbf r(t)=<1,\,2t>dt\ .[/itex]

You will have an odd integrand involving the problematic [itex]\displaystyle e^{\sin^4{y}}\ .[/itex]
 
Last edited:
Does this get me anywhere? It seems to still leave me with something unsolveable.
 
Check for independence of path and use the straight line from (-1,1) to (1,1).
 

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