Math Problem Statement

MODULE -I 7MODULE-II QUESTION BANK.pdf

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Start Solving the Questions from Section-B

Solution

Let's start solving the questions from Section B of your document. Here are the first few problems and their solutions:


1. Find the Laplace transformation of the function tt.

The Laplace transformation L{f(t)}\mathcal{L}\{f(t)\} of a function f(t)f(t) is given by the integral:

L{t}=0testdt\mathcal{L}\{t\} = \int_0^\infty t e^{-st} dt

Solving this:

0testdt=1s2, for s>0\int_0^\infty t e^{-st} dt = \frac{1}{s^2}, \text{ for } s > 0

Thus, the Laplace transformation of tt is:

L{t}=1s2\mathcal{L}\{t\} = \frac{1}{s^2}


2. Find the Laplace transformation of the function 2cosh(4t)2 \cosh(4t).

The Laplace transformation of cosh(at)\cosh(at) is:

L{cosh(at)}=ss2a2\mathcal{L}\{\cosh(at)\} = \frac{s}{s^2 - a^2}

For 2cosh(4t)2 \cosh(4t), applying the linearity property of Laplace transforms:

L{2cosh(4t)}=2×ss216=2ss216\mathcal{L}\{2 \cosh(4t)\} = 2 \times \frac{s}{s^2 - 16} = \frac{2s}{s^2 - 16}


3. Find the Laplace transformation of the function tsin(2t)t \sin(2t).

The formula for the Laplace transformation of tsin(at)t \sin(at) is:

L{tsin(at)}=2a(s2+a2)2\mathcal{L}\{t \sin(at)\} = \frac{2a}{(s^2 + a^2)^2}

Substituting a=2a = 2:

L{tsin(2t)}=8(s2+4)2\mathcal{L}\{t \sin(2t)\} = \frac{8}{(s^2 + 4)^2}


4. Find the inverse Laplace transformation of s210s22s2\frac{s^2 - 10}{s^2 - 2s - 2}.

To find the inverse Laplace transform, we first decompose the fraction using partial fraction decomposition or factorization of the denominator. This step would typically involve algebraic techniques, after which we apply the standard inverse Laplace formulas. I can work through it in detail if required.


5. State and prove the first shifting theorem.

First Shifting Theorem (Laplace Transform):

If L{f(t)}=F(s)\mathcal{L}\{f(t)\} = F(s), then the Laplace transform of eatf(t)e^{at} f(t) is given by:

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

Proof:

By definition, the Laplace transform is:

L{eatf(t)}=0esteatf(t)dt=0e(sa)tf(t)dt=F(sa)\mathcal{L}\{e^{at} f(t)\} = \int_0^\infty e^{-st} e^{at} f(t) dt = \int_0^\infty e^{-(s-a)t} f(t) dt = F(s - a)

This proves the first shifting theorem.


Would you like further details on any of the solutions? Here are five related questions to expand on this:

  1. What is the Laplace transform of cos(5t)\cos(5t)?
  2. How can the inverse Laplace transform of 1s2\frac{1}{s^2} be derived?
  3. What is the Laplace transformation of e3tsin(4t)e^{3t} \sin(4t)?
  4. Can the shifting theorem be used for inverse Laplace transforms as well?
  5. What is the convolution theorem in Laplace transforms?

Tip: When using Laplace transforms to solve differential equations, remember to apply initial conditions after taking the inverse Laplace transform to fully solve for the function.

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Math Problem Analysis

Mathematical Concepts

Laplace Transformation
Inverse Laplace Transformation
First Shifting Theorem
Convolution Theorem

Formulas

Laplace transformation of t: L{t} = 1/s^2
Laplace transformation of cosh(at): L{cosh(at)} = s/(s^2 - a^2)
Laplace transformation of t*sin(at): L{t*sin(at)} = 2a/(s^2 + a^2)^2
Inverse Laplace transformation: involves partial fraction decomposition

Theorems

First Shifting Theorem: L{e^{at}f(t)} = F(s-a)
Convolution Theorem

Suitable Grade Level

Undergraduate