Math Problem Statement

Using Laplace transform, prove that \int_0^\infty \frac{\sin t}{t} dt = \frac{\pi}{2}.

Solution

The image contains the following mathematical problem:

Using Laplace transform, prove that

0sinttdt=π2\int_0^\infty \frac{\sin t}{t} \, dt = \frac{\pi}{2}

Let's solve it step by step using the Laplace transform approach.

Solution Outline:

  1. Step 1: Recognize the Integral
    The integral 0sinttdt\int_0^\infty \frac{\sin t}{t} \, dt is a classic improper integral known as the Dirichlet integral, which equals π2\frac{\pi}{2}.

  2. Step 2: Define a function involving the Laplace transform
    To use the Laplace transform, we introduce a decaying exponential function, such as este^{-st}, which will allow the use of the Laplace transform and remove the problematic improper limits.

    Consider: I(s)=0sinttestdtI(s) = \int_0^\infty \frac{\sin t}{t} e^{-st} \, dt Here, s>0s > 0 is a parameter that ensures convergence of the integral.

  3. Step 3: Solve the integral I(s)I(s) using the known Laplace transform
    The integral involving sint/t\sin t / t has a known result in the Laplace transform tables: L{sintt}=tan1(1s)\mathcal{L}\left\{ \frac{\sin t}{t} \right\} = \tan^{-1}\left( \frac{1}{s} \right) Thus, we can write: I(s)=tan1(1s)I(s) = \tan^{-1}\left( \frac{1}{s} \right)

  4. Step 4: Find the limit as s0s \to 0
    To recover the original integral, we now take the limit as s0s \to 0: lims0I(s)=lims0tan1(1s)=π2\lim_{s \to 0} I(s) = \lim_{s \to 0} \tan^{-1}\left( \frac{1}{s} \right) = \frac{\pi}{2}

Thus, we have shown that: 0sinttdt=π2\int_0^\infty \frac{\sin t}{t} \, dt = \frac{\pi}{2}

Let me know if you need further details or have any questions!

Here are 5 related questions:

  1. How do we find the Laplace transform of more complex functions like sint/t\sin t / t?
  2. What are the properties of Laplace transforms that make them useful in solving integrals?
  3. How do we handle improper integrals without the Laplace transform method?
  4. Can the Laplace transform be used to solve other types of improper integrals?
  5. What other applications do improper integrals have in mathematical physics?

Tip: The Laplace transform is especially helpful when dealing with improper integrals and differential equations because it transforms problems into a simpler algebra

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Math Problem Analysis

Mathematical Concepts

Laplace Transform
Improper Integrals

Formulas

\mathcal{L}\left\{ \frac{\sin t}{t} \right\} = \tan^{-1}\left( \frac{1}{s} \right)

Theorems

Dirichlet Integral
Laplace Transform

Suitable Grade Level

University Level (Calculus or Mathematical Physics)