Solve Stoke's Theorem with Contour C and Vector Field F for Calculus Homework

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Homework Help Overview

The discussion revolves around applying Stokes' Theorem to a vector field defined by a line integral over a contour formed by three curves. The problem involves determining the correct setup for the vector field and the limits of integration.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the definition of the vector field and the application of Stokes' Theorem. There are questions regarding the limits of integration and the interpretation of the notation used in the vector field.

Discussion Status

Some participants have pointed out potential errors in the original poster's limits of integration and notation. Clarifications have been made regarding the interpretation of the sine function in the vector field.

Contextual Notes

There is a noted ambiguity in the notation used for the sine function, which has led to confusion in the discussion. Additionally, the original poster acknowledges a mistake in the range of integration.

null void
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Homework Statement



\oint_C{(x^2 + 2y + sin x^2)dx + (x + y + cos y^2)dy}

the contour C formed by 3 curves:
C(x,y) = \begin{cases}x=0, \quad from (0,0) to (0,5)\\y = 5 - x^2,\quad from(0,5) to (2,1) \\ 4y = x^2, \quad from(2,1) to (0,0)\end{cases}

and the Stoke Theorem:
\oint_C \vec F \, d\vec r = \iint_S \, curl \, \vec F \, d\vec S \\= \iint_S \, curl \, \vec F \cdot \vec n \, dS

The Attempt at a Solution



So in this problem, can I say the vector field, F as follow?
\vec F = <x^2 + 2y + sin x^2 ,\,\, x + y + cos y^2, \,\, 0>
then
\oint_C \vec F \, d\vec r = \iint_S \, curl \, \vec F \, d\vec S \\ = \int_0^5 \int_\frac{x^2}{4}^{5-x^2} -1\, dy\, dx \\ = 27.0833

but probably there is something wrong in there, because the answer is 20/3
 
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Your x only ranges from 0 to 2, not 0 to 5.
 
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Oh yeah, what a silly mistake, thanks.
 
null void said:

Homework Statement



\oint_C{(x^2 + 2y + sin x^2)dx + (x + y + cos y^2)dy}

the contour C formed by 3 curves:
C(x,y) = \begin{cases}x=0, \quad from (0,0) to (0,5)\\y = 5 - x^2,\quad from(0,5) to (2,1) \\ 4y = x^2, \quad from(2,1) to (0,0)\end{cases}

and the Stoke Theorem:
\oint_C \vec F \, d\vec r = \iint_S \, curl \, \vec F \, d\vec S \\= \iint_S \, curl \, \vec F \cdot \vec n \, dS

The Attempt at a Solution



So in this problem, can I say the vector field, F as follow?
\vec F = <x^2 + 2y + sin x^2 ,\,\, x + y + cos y^2, \,\, 0>
then
\oint_C \vec F \, d\vec r = \iint_S \, curl \, \vec F \, d\vec S \\ = \int_0^5 \int_\frac{x^2}{4}^{5-x^2} -1\, dy\, dx \\ = 27.0833

but probably there is something wrong in there, because the answer is 20/3

Your notation is ambiguous and confusing: does ##sin x^2## mean ##\sin(x^2)## or ##\sin^2 x = (\sin x)^2##?
 
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Ray Vickson said:
Your notation is ambiguous and confusing: does ##sin x^2## mean ##\sin(x^2)## or ##\sin^2 x = (\sin x)^2##?
it is sin(x^2), i will make it clear next time
 

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