/*! This file is auto-generated */ .wp-block-button__link{color:#fff;background-color:#32373c;border-radius:9999px;box-shadow:none;text-decoration:none;padding:calc(.667em + 2px) calc(1.333em + 2px);font-size:1.125em}.wp-block-file__button{background:#32373c;color:#fff;text-decoration:none} Problem 27 Integrate \(f\) over the given c... [FREE SOLUTION] | 91Ó°ÊÓ

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Integrate \(f\) over the given curve. $$f(x, y)=x^{3} / y, \quad C: \quad y=x^{2} / 2, \quad 0 \leq x \leq 2$$

Short Answer

Expert verified
The integral of the function over the curve is 4.

Step by step solution

01

Parameterize the Curve

The curve is given by the equation \(y = \frac{x^2}{2}\). Here, the parameter \(x\) itself can be used, so let \(x = t\) and \(y = \frac{t^2}{2}\). For the given range of \(x\), \(t\) varies from 0 to 2.
02

Express the Function f in Terms of t

Substitute \(x = t\) and \(y = \frac{t^2}{2}\) into the function \(f(x, y) = \frac{x^3}{y}\). This gives \(f(t) = \frac{t^3}{\frac{t^2}{2}} = 2t\).
03

Calculate the Line Integral

The line integral over the curve is given by \(\int_C f(x, y) \, ds\). We parameterized as \(t\), so the integral becomes \(\int_{0}^{2} 2t \sqrt{1 + (dx/dt)^2} \, dt\). Since \(dx/dt = 1\) and the factor due to the derivative of \(y\) as a function of \(x\) cancels out, we integrate: \(\int_{0}^{2} 2t \, dt\).
04

Integrate with Respect to t

Perform the integration: \(\int_{0}^{2} 2t \, dt = \left[ t^2 \right]_{0}^{2} = 2^2 = 4\).
05

Interpret the Result

The result of the integral, which is 4, represents the line integral of the function along the curve from \(x = 0\) to \(x = 2\).

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Parametric Equations
Parametric equations are an essential tool in mathematics, especially when dealing with curves and calculating line integrals.
They allow us to define a path with variables called parameters. In our exercise, the curve is given by the equation \(y = \frac{x^2}{2}\). One of the simplest ways to parameterize this is to let \(x = t\), the parameter, which directly represents the horizontal coordinate.
This choice leads to \(y = \frac{t^2}{2}\), giving us a two-variable representation with respect to one parameter, \(t\). Parameterizing like this helps in converting a complex curve into an algebraically manageable form.
Especially in line integrals, breaking down the components in this manner enables straightforward calculations and helps us to visualize the path of integration as it passes through various points on the curve.
Using different variables as parameters also provides flexibility in handling complex situations involving multiple curves or surfaces, but choosing the simplest parameter often simplifies calculus operations greatly.
Integration Techniques
Integrating over curves, referred to as line integrals, often requires a specific set of techniques.
For our exercise, after parameterizing the curve with \(x = t\) and \(y = \frac{t^2}{2}\), we need to express the function \(f(x, y) = \frac{x^3}{y}\) in terms of the parameter \(t\).
  • This substitution changes the function into a simpler form like \(f(t) = 2t\).
  • The parameterization simplifies the variables and aligns the function with the path of integration.
The next step is to set up the integral with respect to \(t\). The integral becomes \[\int_{0}^{2} 2t \, \text{d}t\] where we have assumed \(\sqrt{1 + (dx/dt)^2}\) factor simplifies because \(dx/dt\) equals 1.
This simplification is often possible in calculus when the parameterization is correctly chosen and when the curve's path is straightforward.
The focus here is on proper substitution and simplification, which are key integration techniques needed in calculus for solving complex problems efficiently.
Calculus
Calculus is often described as the mathematics of change and motion, and line integrals are a great demonstration of its power.
In calculus, line integrals extend the idea of integration to integrate functions along curves rather than over intervals.
  • This allows us to calculate quantities like work done along a path or even the length of the curve itself.
  • In parametric form, calculus provides a powerful framework for evaluating these integrals.
In our scenario, we perform a simple integration to evaluate the line integral:\[\int_{0}^{2} 2t \, dt = \left[ t^2 \right]_{0}^{2} = 4\]This result tells us that the total contribution of the function \(f\) over our specified curve is 4.
Such calculations underscore the effectiveness of calculus in connecting algebraic expressions with geometric interpretations.
By understanding how to use calculus in this way, learners can better appreciate its application in physics, engineering, and other scientific fields where dynamic change plays a crucial role.

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Most popular questions from this chapter

Use a parametrization to express the area of the surface as a double integral. Then evaluate the integral. (There are many correct ways to set up the integrals, so your integrals may not be the same as those in the back of the book. They should have the same values, however.) The portion of the cylinder \(x^{2}+z^{2}=\) 10 between the planes \(y=-1\) and \(y=1\)

a. A torus of revolution (doughnut) is obtained by rotating a circle \(C\) in the \(x z\) -plane about the \(z\) -axis in space. (See the accompanying figure.) If \(C\) has radius \(r>0\) and center \((R, 0,0),\) show that a parametrization of the torus is $$\begin{aligned}\mathbf{r}(u, v)=&((R+r \cos u) \cos v) \mathbf{i} \\\&+((R+r \cos u) \sin v) \mathbf{j}+(r \sin u) \mathbf{k}\end{aligned}$$ where \(0 \leq u \leq 2 \pi\) and \(0 \leq v \leq 2 \pi\) are the angles in the figure.b. Show that the surface area of the torus is \(A=4 \pi^{2} R r\)

Let \(\mathbf{n}\) be the outer unit normal (normal away from the origin) of the parabolic shell $$ S: 4 x^{2}+y+z^{2}=4, \quad y \geq 0$$ and let $$\mathbf{F}=\left(-z+\frac{1}{2+x}\right) \mathbf{i}+\left(\tan ^{-1} y\right)\mathbf{j}+\left(x+\frac{1}{4+z}\right) \mathbf{k}$$ Find the value of $$\iint_{S} \nabla \times \mathbf{F} \cdot \mathbf{n} d \sigma.$$

If a simple closed curve \(C\) in the plane and the region \(R\) it encloses satisfy the hypotheses of Green's Theorem, the area of \(R\) is given by $$\text { Area of } R=\frac{1}{2} \oint_{C} x d y-y d x$$ The reason is that by Equation (4), run backward, $$\begin{aligned} \text { Area of } R &=\iint_{R} d y d x=\iint_{R}\left(\frac{1}{2}+\frac{1}{2}\right) d y d x \\ &=\oint_{C} \frac{1}{2} x d y-\frac{1}{2} y d x \end{aligned}.$$ Use the Green's Theorem area formula given above to find the areas of the regions enclosed by the curves. One arch of the cycloid \(x=t-\sin t, \quad y=1-\cos t\)

Apply Green's Theorem to evaluate the integrals. \(\oint_{C}\left(2 x+y^{2}\right) d x+(2 x y+3 y) d y\) C: Any simple closed curve in the plane for which Green's Theorem holds

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