Chapter 13: Problem 6
Evaluate the line integral, where \(C\) is the given curve. $$\begin{array}{l}{\int_{c} e^{x} d x,} \\ {C \text { is the arc of the curve } x=y^{3} \text { from }(-1,-1) \text { to }(1,1)}\end{array}$$
Short Answer
Expert verified
The line integral evaluates to \(e - \frac{1}{e}\).
Step by step solution
01
Parameterize the Curve
The curve given is \(x = y^3\). To parameterize it from \((-1,-1)\) to \((1,1)\), we can set \(y = t\), where \(t\) ranges from \(-1\) to \(1\). Then, \(x = t^3\). So the parameterization is \(\mathbf{r}(t) = (t^3, t)\) with \(t \in [-1, 1]\).
02
Differentiate x with respect to t
Since \(x = t^3\), differentiate to find \(\frac{dx}{dt} = 3t^2\). This will be used later in calculating the line integral.
03
Express the Integral with Parameterization
Using the parameterization \(\mathbf{r}(t)\), the integral \(\int_C e^x \, dx\) becomes \(\int_{-1}^{1} e^{t^3} \cdot 3t^2 \, dt\).
04
Evaluate the Integral
The integral is \(\int_{-1}^{1} 3t^2 e^{t^3} \, dt\). Let \(u = t^3\), then \(du = 3t^2 \, dt\). The limits change to \(u = (-1)^3 = -1\) when \(t = -1\) and \(u = 1\) when \(t = 1\). Now the integral becomes \(\int_{-1}^{1} e^u \, du\).
05
Compute the Antiderivative
The antiderivative of \(e^u\) is \(e^u\), so we compute \(\left[ e^u \right]_{-1}^{1}\), which is \(e^1 - e^{-1}= e - \frac{1}{e}\).
06
Conclusion
The value of the line integral is calculated as \(e - \frac{1}{e}\).
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Key Concepts
These are the key concepts you need to understand to accurately answer the question.
Parameterization
In calculus, parameterization is a powerful technique used to deal with curves and surfaces by expressing the position along a curve using a single variable, typically denoted as \(t\). This is particularly useful when working with line integrals, where the path of integration is along a curve. In this problem, we have a curve defined by the equation \(x = y^3\). To parameterize the curve from \((-1,-1)\) to \((1,1)\), we substitute a parameter \(t\) for \(y\). Therefore, we set \(y = t\), which naturally leads to \(x = t^3\) by the curve equation.
- The parameter \(t\) ranges from \(-1\) to \(1\).
- The parameterized equations are \(x = t^3\) and \(y = t\).
Antiderivative
Calculating an antiderivative is finding a function whose derivative produces the original function. In this context, when working with line integrals, finding the antiderivative of a transformed integral can simplify the evaluation. Here, the line integral of interest becomes \(\int_{-1}^{1} 3t^2 e^{t^3} \, dt\). We employ the substitution technique, where we let \(u = t^3\). Consequently, the derivative \(du = 3t^2 \, dt\) clearly matches the terms in our integral, allowing a straightforward substitution.
- The integral transforms to \(\int e^u \, du\).
- The antiderivative of \(e^u\) is simply \(e^u\).
Curve Parameterization
Curve parameterization is integral in calculus for converting complex curves into manageable, calculable forms. The idea is to express the coordinates of points on a curve as functions of a single parameter. In this example, we parameterized the curve \(x = y^3\) for \(y\) in the interval \([-1, 1]\).
- The original curve is rewritten as functions of \(t\), providing \(x = t^3\) and \(y = t\).
- This allows step-by-step transformation of the integral into a simpler form.