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Compute the Laplace transform of the given matrix-valued function \(\mathbf{y}(t)\). \(\mathbf{y}(t)=\int_{0}^{t}\left[\begin{array}{c}1 \\ \lambda \\\ e^{-\lambda}\end{array}\right] d \lambda\)

Short Answer

Expert verified
Answer: The Laplace transform of the matrix-valued function \(\mathbf{y}(t)\) is given by \(\mathcal{L}\{\mathbf{y}(t)\} = \left[\begin{array}{c}\frac{1}{s^2} \\\ \frac{2}{s^3} \\\ \frac{1}{s} - \frac{1}{s+1}\end{array}\right]\).

Step by step solution

01

Evaluate the integral

Begin by evaluating the integral element-wise: \(\int_{0}^{t}\left[\begin{array}{c}1 \\\ \lambda \\\ e^{-\lambda}\end{array}\right] d \lambda = \left[\begin{array}{c} \int_{0}^{t} 1 d\lambda \\\ \int_{0}^{t} \lambda d\lambda \\\ \int_{0}^{t} e^{-\lambda} d\lambda \end{array}\right]\) Now we will find each integral: 1. \(\int_{0}^{t} 1 d\lambda = \lambda \Big|_{0}^{t} = t\) 2. \(\int_{0}^{t} \lambda d\lambda = \frac{1}{2}\lambda^2 \Big|_{0}^{t} = \frac{1}{2}t^2\) 3. \(\int_{0}^{t} e^{-\lambda} d\lambda = -e^{-\lambda} \Big|_{0}^{t} = -(e^{-t} - 1)\) So, the result of the integral is: \(\mathbf{y}(t) = \left[\begin{array}{c}t \\\ \frac{1}{2}t^2 \\\ 1-e^{-t}\end{array}\right]\)
02

Apply the Laplace Transform

Now, we will apply the Laplace transform to each entry of the matrix: 1. \(\mathcal{L}\{t\} = \int_{0}^{\infty} t e^{-st} dt = \frac{1}{s^2}\) 2. \(\mathcal{L}\{\frac{1}{2}t^2\} = \int_{0}^{\infty} \frac{1}{2}t^2 e^{-st} dt = \frac{2}{s^3}\) 3. \(\mathcal{L}\{1-e^{-t}\} = \mathcal{L}\{1\} - \mathcal{L}\{e^{-t}\} = \frac{1}{s} - \frac{1}{s+1}\) So, the final result for the Laplace transform of the matrix-valued function is: \(\mathcal{L}\{\mathbf{y}(t)\} = \left[\begin{array}{c}\frac{1}{s^2} \\\ \frac{2}{s^3} \\\ \frac{1}{s} - \frac{1}{s+1}\end{array}\right]\)

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Key Concepts

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

Matrix-valued function
A matrix-valued function is an intriguing concept in mathematics. While most functions yield a single value as the output, a matrix-valued function produces an entire matrix. In our example, \(\mathbf{y}(t)\), we observe this function mapping time, \(t\), to a column matrix.
This is evident in the integral representation:
\(\mathbf{y}(t)=\int_{0}^{t}\left[\begin{array}{c}1 \ \lambda \ e^{-lambda}\end{array}\right] d \lambda\).
Here, each entry in the matrix is a separate function of \(\lambda\), the integral variable.
  • The first entry is constant 1 over the integration.
  • The second entry is the linearly increasing function \(\lambda\), resulting in a simple polynomial after integration.
  • The third entry is the exponential decay function \(e^{-lambda}\), leading to exponential behavior in the solution.
Evaluating such matrix-valued functions involves integrating each entry separately, allowing you to understand the influence of each component on the system.
Such functions are especially useful in representing systems with multiple state variables, such as those found in physics and engineering.
Integral calculus
Integral calculus is a vital part of understanding and computing matrix-valued functions. It allows us to determine the accumulation of quantities, as seen in the solution of \(\mathbf{y}(t) = \int_{0}^{t}\left[\begin{array}{c}1 \ \lambda \ e^{-lambda}\end{array}\right] d \lambda\). The integral provides the total change or accumulation of each component from the starting point (0) to time \(t\).
  • The integral of a constant, like 1, leads to a linear function, which indicates uniform accumulation.
  • For the term \(\lambda\), which varies linearly, the integral is \(\frac{1}{2}\lambda^2\), introducing polynomial growth to the system dynamics.
  • The exponential term \(e^{-lambda}\) provides a more complex result, \(1-e^{-t}\), depicting an asymptotic approach to a limit as \(t\) goes to infinity.
Integral calculus thus converts rate expressions into cumulative ones, crucial in solving real-world problems involving dynamics and change across different systems.
Differential equations
Differential equations form an essential link between calculus and Laplace Transform applications. They often describe how a particular function changes over time. In the realm of solving differential equations, the Laplace Transform is particularly powerful. It helps convert these equations from the time domain to an algebraically solvable form in the s-domain.
  • By transforming derivatives into basic algebraic terms in the s-domain, it simplifies the solution process greatly.
  • Transforming a matrix-valued function like \(\mathbf{y}(t)\) involves separate transformations for each element, as in our computation result:
    \(\mathcal{L}\{t\} = \frac{1}{s^2}, \; \mathcal{L}\{\frac{1}{2}t^2\} = \frac{2}{s^3}, \; \mathcal{L}\{1-e^{-t}\} = \frac{1}{s} - \frac{1}{s+1}\).
By employing the Laplace Transform, differential equations can be tackled with basic algebra, making it a robust tool in engineering and systems analysis where complex dynamic behavior occurs.

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Most popular questions from this chapter

For the linear system defined by the given initial value problem, (a) Determine the system transfer function, \(\Phi(s)\). (b) Determine the Laplace transform of the output, \(Y(s)\), corresponding to the specified input, \(f(t)\). $$ y^{\prime \prime}+4 y^{\prime}+4 y=f(t), \quad y(0)=0, \quad y^{\prime}(0)=0 ; \quad f(t)=t, \quad 0 \leq t<1, \quad f(t+1)=f(t) $$

Use Laplace transforms to solve the given initial value problem. \(\mathbf{y}^{\prime}=\left[\begin{array}{ll}5 & -4 \\ 3 & -2\end{array}\right] \mathbf{y}, \quad \mathbf{y}(0)=\left[\begin{array}{l}3 \\\ 2\end{array}\right]\)

A lake containing 50 million gal of fresh water has a stream flowing through it. Water enters the lake at a constant rate of \(5 \mathrm{million~gal/day~and~leaves~at~the~same~}\) rate. At some initial time, an upstream manufacturer begins to discharge pollutants into the feeder stream. Each day, during the hours from 8 A.M. to 8 P.M., the stream has a pollutant concentration of \(1 \mathrm{mg} / \mathrm{gal}\left(10^{-6} \mathrm{~kg} / \mathrm{gal}\right)\); at other times, the stream feeds in fresh water. Assume that a well-stirred mixture leaves the lake and that the manufacturer operates seven days per week. (a) Let \(t=0\) denote the instant that pollutants first enter the lake. Let \(q(t)\) denote the amount of pollutant (in kilograms) present in the lake at time \(t\) (in days). Use a "conservation of pollutant" principle (rate of change \(=\) rate in \(-\) rate out) to formulate the initial value problem satisfied by \(q(t)\). (b) Apply Laplace transforms to the problem formulated in (a) and determine \(Q(s)=\mathcal{L}\\{q(t)\\} .\) (c) Determine \(q(t)=\mathcal{L}^{-1}\\{Q(s)\\}\), using the ideas of Example 2 . In particular, what is \(q(t)\) for \(1 \leq t<2\), the second day of manfacturing?

Give the form of the partial fraction expansion for the given rational function \(F(s)\). You need not evaluate the constants in the expansion. However, if the denominator of \(F(s)\) contains irreducible quadratic factors of the form \(s^{2}+2 \alpha s+\beta^{2}, \beta^{2}>\alpha^{2}\), complete the square and rewrite this factor in the form \((s+\alpha)^{2}+\omega^{2}\). $$F(s)=\frac{s^{2}+5 s-3}{\left(s^{2}+16\right)(s-2)}$$

Compute the Laplace transform of the given matrix-valued function \(\mathbf{y}(t)\). \(\mathbf{y}(t)=\frac{d}{d t}\left[\begin{array}{c}e^{-t} \cos 2 t \\ 0 \\\ t+e^{t}\end{array}\right]\)

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