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Question
Math
Posted 5 months ago

Suppose we have a vector field f(x,y)=(y,x)f(x, y)=(-y, x) and a curve CC that is parameterized by α(t)=(cos(t),sin(t))\alpha(t)=(\cos (t), \sin (t)) for 0<t<2π0<t<2 \pi.

What is the line integral of ff along CC ?
Cfdα=
\int_{C} f \cdot d \alpha=

\square
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Answer from Sia
Posted 5 months ago
Solution by Steps
step 1
To find the line integral of the vector field f(x,y)=(y,x)f(x, y) = (-y, x) along the curve CC parameterized by α(t)=(cos(t),sin(t))\alpha(t) = (\cos(t), \sin(t)), we first need to compute dαd\alpha
step 2
The differential dαd\alpha is given by the derivative of α(t)\alpha(t) with respect to tt, which is dα=(sin(t),cos(t))dtd\alpha = (-\sin(t), \cos(t))dt
step 3
We then compute the dot product fdα=(y,x)(sin(t),cos(t))dtf \cdot d\alpha = (-y, x) \cdot (-\sin(t), \cos(t))dt. Substituting x=cos(t)x = \cos(t) and y=sin(t)y = \sin(t), we get fdα=(sin2(t)+cos2(t))dtf \cdot d\alpha = (\sin^2(t) + \cos^2(t))dt
step 4
Since sin2(t)+cos2(t)=1\sin^2(t) + \cos^2(t) = 1, the dot product simplifies to fdα=dtf \cdot d\alpha = dt
step 5
The line integral Cfdα\int_{C} f \cdot d\alpha is then the integral of dtdt over the interval 0<t<2π0 < t < 2\pi
step 6
Evaluating the integral, we get 02πdt=2π0=2π\int_{0}^{2\pi} dt = 2\pi - 0 = 2\pi
[1] Answer
2π2\pi
Key Concept
Line Integral of a Vector Field
Explanation
The line integral of a vector field along a curve is found by taking the dot product of the vector field and the differential of the curve's parameterization, then integrating over the specified interval.

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