Math Problem Statement

Find the Laplace transform of ( f(t) = e^{2t} \sin(3t) ) by first shifting

Solution

To find the Laplace transform of f(t)=e2tsin(3t)f(t) = e^{2t} \sin(3t), we can use the Laplace transform shifting theorem. The shifting theorem states that if:

L{eatf(t)}(s)=F(sa)\mathcal{L}\{e^{at} f(t)\}(s) = F(s-a)

We will start by finding the Laplace transform of sin(3t)\sin(3t) and then apply the shifting rule.

Step 1: Find the Laplace transform of sin(3t)\sin(3t)

The Laplace transform of sin(bt)\sin(bt) is:

L{sin(bt)}(s)=bs2+b2\mathcal{L}\{\sin(bt)\}(s) = \frac{b}{s^2 + b^2}

For sin(3t)\sin(3t), we substitute b=3b = 3:

L{sin(3t)}(s)=3s2+9\mathcal{L}\{\sin(3t)\}(s) = \frac{3}{s^2 + 9}

Step 2: Apply the shifting theorem

Now, using the shifting theorem for e2tsin(3t)e^{2t} \sin(3t), we replace ss with s2s - 2 in the Laplace transform of sin(3t)\sin(3t):

L{e2tsin(3t)}(s)=3(s2)2+9\mathcal{L}\{e^{2t} \sin(3t)\}(s) = \frac{3}{(s - 2)^2 + 9}

Thus, the Laplace transform of f(t)=e2tsin(3t)f(t) = e^{2t} \sin(3t) is:

L{f(t)}(s)=3(s2)2+9\mathcal{L}\{f(t)\}(s) = \frac{3}{(s - 2)^2 + 9}

Would you like more details or have any questions?

Here are 5 related questions to explore further:

  1. How do you apply the Laplace transform to exponential functions?
  2. What is the inverse Laplace transform of 3(s2)2+9\frac{3}{(s - 2)^2 + 9}?
  3. How does the shifting theorem work for different kinds of functions?
  4. Can you find the Laplace transform of e3tcos(4t)e^{3t} \cos(4t)?
  5. How does the convolution theorem relate to the Laplace transform?

Tip: Always check for initial conditions when applying the Laplace transform to differential equations!

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Math Problem Analysis

Mathematical Concepts

Laplace Transform
Exponential Functions
Trigonometric Functions

Formulas

Laplace transform of \sin(bt): \mathcal{L}\{\sin(bt)\}(s) = \frac{b}{s^2 + b^2}
Shifting theorem: \mathcal{L}\{e^{at} f(t)\}(s) = F(s-a)

Theorems

Shifting Theorem of Laplace Transform

Suitable Grade Level

Undergraduate