Math Problem Statement

using the first derivative property of laplace transform, find f'(t)=3e^{2t} + 4\sin(3t)

Solution

To solve for f(t)=3e2t+4sin(3t)f'(t) = 3e^{2t} + 4\sin(3t) using the first derivative property of the Laplace transform, we will proceed step by step.

Step 1: Recall the first derivative property of the Laplace transform

The first derivative property states that:

L{f(t)}=sF(s)f(0)\mathcal{L} \{ f'(t) \} = sF(s) - f(0)

where F(s)F(s) is the Laplace transform of f(t)f(t), and f(0)f(0) is the initial condition of f(t)f(t) at t=0t = 0.

Step 2: Express f(t)f'(t)

Given: f(t)=3e2t+4sin(3t)f'(t) = 3e^{2t} + 4\sin(3t)

We need to take the Laplace transform of each term.

(a) Laplace Transform of 3e2t3e^{2t}

Using the Laplace transform of eate^{at}, which is L{eat}=1sa\mathcal{L} \{ e^{at} \} = \frac{1}{s - a}, we get:

L{3e2t}=31s2=3s2\mathcal{L} \{ 3e^{2t} \} = 3 \cdot \frac{1}{s - 2} = \frac{3}{s - 2}

(b) Laplace Transform of 4sin(3t)4\sin(3t)

Using the Laplace transform of sin(at)\sin(at), which is L{sin(at)}=as2+a2\mathcal{L} \{ \sin(at) \} = \frac{a}{s^2 + a^2}, we get:

L{4sin(3t)}=43s2+9=12s2+9\mathcal{L} \{ 4\sin(3t) \} = 4 \cdot \frac{3}{s^2 + 9} = \frac{12}{s^2 + 9}

Step 3: Add the Laplace transforms

Now, the Laplace transform of f(t)f'(t) is the sum of the transforms:

L{f(t)}=3s2+12s2+9\mathcal{L} \{ f'(t) \} = \frac{3}{s - 2} + \frac{12}{s^2 + 9}

Step 4: Use the first derivative property to find L{f(t)}\mathcal{L} \{ f(t) \}

Using the property L{f(t)}=sF(s)f(0)\mathcal{L} \{ f'(t) \} = sF(s) - f(0), and assuming f(0)=0f(0) = 0 (if no initial condition is given), we have:

sF(s)=3s2+12s2+9sF(s) = \frac{3}{s - 2} + \frac{12}{s^2 + 9}

Thus:

F(s)=3s2+12s2+9sF(s) = \frac{\frac{3}{s - 2} + \frac{12}{s^2 + 9}}{s}

This expression represents the Laplace transform of f(t)f(t).

Conclusion

Using the first derivative property of the Laplace transform, we found that the Laplace transform of the original function f(t)f(t) is:

F(s)=3s(s2)+12s(s2+9)F(s) = \frac{3}{s(s - 2)} + \frac{12}{s(s^2 + 9)}

If you'd like to go further and invert the transform to find f(t)f(t), or need more details on any step, let me know!


Do you want to see the details of the inverse transform or have any specific questions?

Here are some related problems you could explore:

  1. Find the inverse Laplace transform of 3s(s2)\frac{3}{s(s - 2)}.
  2. Use the Laplace transform to solve f(t)=3e2t+4sin(3t)f''(t) = 3e^{2t} + 4\sin(3t) with f(0)=0f(0) = 0, f(0)=1f'(0) = 1.
  3. Solve a second-order differential equation using Laplace transforms.
  4. Explore the Laplace transform of eatcos(bt)e^{at} \cos(bt).
  5. How does the second derivative property of the Laplace transform work?

Tip: The Laplace transform is particularly useful for solving differential equations with initial conditions, as it simplifies them into algebraic equations.

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Math Problem Analysis

Mathematical Concepts

Laplace Transform
First Derivative Property
Differential Equations

Formulas

Laplace transform of e^{at}: \mathcal{L} \{ e^{at} \} = \frac{1}{s - a}
Laplace transform of \sin(at): \mathcal{L} \{ \sin(at) \} = \frac{a}{s^2 + a^2}
First derivative property: \mathcal{L} \{ f'(t) \} = sF(s) - f(0)

Theorems

First Derivative Theorem of Laplace Transforms

Suitable Grade Level

Undergraduate Math or Advanced High School