Is the Parameterization Correct in Leithold's Stokes' Theorem Problem?

In summary, the discussion revolves around the accuracy of the parameterization used in Leithold's Stokes' Theorem problem. It critically evaluates whether the chosen parameterization aligns with the conditions required for Stokes' Theorem to hold true. The analysis highlights potential discrepancies and emphasizes the importance of proper parameterization in applying the theorem correctly, ultimately leading to a better understanding of the problem's underlying mathematical principles.
  • #1
runinfang
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0
Homework Statement
Verify Stokes' theorem in the plane where f(x,y)=y2i+x2j
and the region formed is bounded by the circle (x^2+y^2=4).
Relevant Equations
Stokes' theorem in the plane
"Let \( M \) and \( N \) be the functions, \( C \) be the curve, and \( R \) be the region defined as in Green's theorem. If \( \mathbf{F}(x, y) = M(x, y)\mathbf{i} + N(x, y)\mathbf{j} \) and \( \mathbf{T}(s) \) is the unit tangent vector to \( C \) at \( P \), where \( s \) units is the arc length of \( C \) measured from a point \( P_0 \) to \( P \), then:

\[
\oint_C \mathbf{F} \cdot \mathbf{T} \, ds = \iint_R (\text{curl } \mathbf{F}) \cdot \mathbf{k} \, dA
\]"
The question is a problem from Leithold's calculus book. I didn't understand the (x = 5 \cos(t)). Shouldn't it be (x = 2 cos(t))? I'm referring to item b.
1710974059690.png

i tried this way. i don't know what is wrong.
1710975133627.png
 
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  • #2
runinfang said:
Homework Statement: Verify Stokes' theorem in the plane where f(x,y)=y2i+x2j
and the region formed is bounded by the circle (x^2+y^2=4).
Relevant Equations: Stokes' theorem in the plane
"Let \( M \) and \( N \) be the functions, \( C \) be the curve, and \( R \) be the region defined as in Green's theorem. If \( \mathbf{F}(x, y) = M(x, y)\mathbf{i} + N(x, y)\mathbf{j} \) and \( \mathbf{T}(s) \) is the unit tangent vector to \( C \) at \( P \), where \( s \) units is the arc length of \( C \) measured from a point \( P_0 \) to \( P \), then:

\[
\oint_C \mathbf{F} \cdot \mathbf{T} \, ds = \iint_R (\text{curl } \mathbf{F}) \cdot \mathbf{k} \, dA
\]"

The question is a problem from Leithold's calculus book. I didn't understand the (x = 5 \cos(t)). Shouldn't it be (x = 2 cos(t))? I'm referring to item b.
View attachment 342076
i tried this way. i don't know what is wrong.
View attachment 342077
Please wrap your text with ## or otherwise to render Latex, make your text more readable.
 

FAQ: Is the Parameterization Correct in Leithold's Stokes' Theorem Problem?

What is Leithold's Stokes' Theorem Problem?

Leithold's Stokes' Theorem Problem typically involves applying Stokes' Theorem, which relates a surface integral over a surface to a line integral over its boundary. The problem usually requires verifying that the parameterization of the surface and its boundary is correct to ensure accurate application of the theorem.

How do you verify the parameterization of the surface in Stokes' Theorem?

To verify the parameterization of the surface, you need to ensure that the parameterization correctly describes the surface in question. This involves checking the bounds of the parameters, ensuring the surface is smooth and continuous, and verifying that the parameterization covers the entire surface without overlap or gaps.

What are common mistakes in parameterizing surfaces for Stokes' Theorem?

Common mistakes include incorrect bounds for the parameters, overlapping or incomplete coverage of the surface, and not accounting for the orientation of the surface. Ensuring the normal vector points in the correct direction is also crucial for the correct application of Stokes' Theorem.

How does the orientation of the surface affect Stokes' Theorem?

The orientation of the surface is critical in Stokes' Theorem because it determines the direction of the normal vector. The orientation must be consistent with the direction of traversal around the boundary curve. If the orientation is incorrect, the resulting integral may have the wrong sign or be entirely incorrect.

Can you provide an example of a correctly parameterized surface for Stokes' Theorem?

Consider a hemisphere of radius \( R \) centered at the origin, parameterized by spherical coordinates. The surface can be parameterized as \( \vec{r}(\theta, \phi) = R \sin\theta \cos\phi \, \hat{i} + R \sin\theta \sin\phi \, \hat{j} + R \cos\theta \, \hat{k} \) with \( 0 \leq \theta \leq \pi/2 \) and \( 0 \leq \phi < 2\pi \). This parameterization covers the entire hemisphere and ensures the surface is smooth and continuous.

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