Math Problem Statement

find laplace transform of tcos(2t)

Solution

The Laplace transform of tcos(2t)t \cos(2t) can be found using the formula:

L{tf(t)}=dds(L{f(t)})\mathcal{L} \{ t f(t) \} = -\frac{d}{ds} \left( \mathcal{L} \{ f(t) \} \right)

where f(t)=cos(2t)f(t) = \cos(2t) and L{cos(2t)}=ss2+4\mathcal{L} \{ \cos(2t) \} = \frac{s}{s^2 + 4}.

Now, differentiate ss2+4\frac{s}{s^2 + 4} with respect to ss:

= \frac{s^2 + 4 - 2s^2}{(s^2 + 4)^2} = \frac{-s^2 + 4}{(s^2 + 4)^2}$$ Thus, the Laplace transform of $$t \cos(2t)$$ is: $$\mathcal{L} \{ t \cos(2t) \} = -\frac{-s^2 + 4}{(s^2 + 4)^2} = \frac{s^2 - 4}{(s^2 + 4)^2}$$ So, the Laplace transform of $$t \cos(2t)$$ is: $$\mathcal{L} \{ t \cos(2t) \} = \frac{s^2 - 4}{(s^2 + 4)^2}$$ Would you like more details or further clarification? Here are 5 related questions: 1. How do you find the Laplace transform of $$t \sin(3t)$$? 2. What is the Laplace transform of a general function $$t^n \cos(at)$$? 3. How can you apply the convolution theorem to Laplace transforms? 4. What is the inverse Laplace transform of $$\frac{s}{s^2 + a^2}$$? 5. Can you explain the shifting property in Laplace transforms? **Tip:** Differentiation in the Laplace domain is often used to handle expressions with time multiplication, so memorizing this technique is helpful.

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Math Problem Analysis

Mathematical Concepts

Laplace Transform
Differentiation
Trigonometric Functions

Formulas

Laplace transform of t f(t): L{t f(t)} = -d/ds (L{f(t)})
Laplace transform of cos(at): L{cos(at)} = s / (s^2 + a^2)

Theorems

Differentiation Property of Laplace Transform

Suitable Grade Level

Undergraduate (Calculus/Engineering Math)