Calculating a Line Integral with Greens Theorem

In summary, the problem is to calculate the line integral \oint _c xdy-ydx where C is the straight line segment from (x_1 , y_1) to (x_2 , y_2). It was initially thought that Green's theorem could be used, but upon further examination it is clear that the line integral itself can be solved without the use of Green's theorem.
  • #1
gtfitzpatrick
379
0

Homework Statement



Calculate [itex]\oint _c xdy-ydx [/itex] where C is the straight line segment from[itex] (x_1 , y_1) to (x_2 , y_2)[/itex]

Homework Equations


The Attempt at a Solution



so from Greens theorem I get [itex]\oint _c xdy-ydx [/itex] = [itex]\int\int \frac{\partial x}{\partial x} + \frac{\partial y}{\partial y} dxdy[/itex]

=2 [itex]\int^{x_2}_{x_1}\int^{y_2}_{y_1} dydx[/itex]
=2[[itex](y_2 - y_1)(x_2 - x_1)[/itex] ]
 
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  • #2
gtfitzpatrick said:

Homework Statement



Calculate [itex]\oint _c xdy-ydx [/itex] where C is the straight line segment from[itex] (x_1 , y_1) to (x_2 , y_2)[/itex]

Homework Equations





The Attempt at a Solution



so from Greens theorem I get [itex]\oint _c xdy-ydx [/itex] = [itex]\int\int \frac{\partial x}{\partial x} + \frac{\partial y}{\partial y} dxdy[/itex]

=2 [itex]\int^{x_2}_{x_1}\int^{y_2}_{y_1} dydx[/itex]
=2[[itex](y_2 - y_1)(x_2 - x_1)[/itex] ]

For Green's theorem you need a line integral along a curve which encloses an area. You don't have that so Green's theorem has nothing to do with this problem. Just work the line integral itself out.
 
  • #3
Hi LCkutz,
Aghhh so he threw it in as a trick question into the greens theorem section. Sneeky!
Thanks LC
 

1. What is a line integral?

A line integral is a type of integral in multivariable calculus that involves calculating the total value of a function along a curve or path.

2. What is Green's Theorem?

Green's Theorem is a mathematical theorem that relates the line integral of a two-dimensional vector field over a closed curve to the double integral of its potential function over the region enclosed by the curve.

3. How do you calculate a line integral using Green's Theorem?

To calculate a line integral using Green's Theorem, you first need to determine the components of the vector field and the region enclosed by the curve. Then, you can use the formula provided by Green's Theorem to evaluate the double integral, which will give you the value of the line integral.

4. What are the benefits of using Green's Theorem to calculate line integrals?

One of the main benefits of using Green's Theorem is that it allows you to calculate a line integral over a closed curve by evaluating a double integral, which can often be easier and more efficient. Additionally, Green's Theorem is a powerful tool in solving many problems in physics and engineering that involve calculating line integrals.

5. Are there any limitations or special cases when using Green's Theorem for line integrals?

Yes, there are a few limitations and special cases to be aware of when using Green's Theorem for line integrals. Green's Theorem only applies to two-dimensional vector fields and closed curves, so it cannot be used for line integrals in three dimensions. Additionally, the region enclosed by the curve must be simply connected, meaning that it does not contain any holes or self-intersections.

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