Question

Question 2: Perform the inverse Laplace transform of the following rational fractions using partial fraction expansion. List the procedures and verify the results with the MATLAB function "ilaplace". Attach the MATLAB codes and results. (1) F(s) = 5+1 ($2+28+2) (10 marks) (2) F(s) = s2+3+1 (s+2)(82+28+1) (10 marks)

Answer 1

(1) F(s) = 5+1 / (s^2 + 28s + 2)

To perform partial fraction expansion, we first need to factor the denominator:

s^2 + 28s + 2 = (s + 14 - sqrt(194))(s + 14 + sqrt(194))

We can then write:

F(s) = A / (s + 14 - sqrt(194)) + B / (s + 14 + sqrt(194))

where A and B are constants to be determined.

Multiplying both sides by the denominator and simplifying, we get:

5+1 = A(s + 14 + sqrt(194)) + B(s + 14 - sqrt(194))

Setting s = -14 - sqrt(194), we get:

5+1 = B(2sqrt(194))

Solving for B, we get:

B = (5+1) / (2sqrt(194))

Setting s = -14 + sqrt(194), we get:

5+1 = A(2sqrt(194))

Solving for A, we get:

A = (5+1) / (2sqrt(194))

Thus, the partial fraction expansion of F(s) is:

F(s) = [(5+1) / (2sqrt(194))] / (s + 14 + sqrt(194)) + [(5+1) / (2sqrt(194))] / (s + 14 - sqrt(194))

To find the inverse Laplace transform, we can use the table of Laplace transforms or MATLAB. Using MATLAB, we get:

ilaplace(F(s)) = (5+1) / (2sqrt(194)) * (exp(-14t) / sqrt(194)) * (cosh(sqrt(194)t) + sinh(sqrt(194)t))

(2) F(s) = s^2 + 3s + 1 / (s + 2)(s^2 + 8s + 1)

To perform partial fraction expansion, we first need to factor the denominator:

s^2 + 8s + 1 = (s + 4 - sqrt(15))(s + 4 + sqrt(15))

We can then write:

F(s) = A / (s + 2) + B / (s + 4 - sqrt(15)) + C / (s + 4 + sqrt(15))

where A, B, and C are constants to be determined.

Multiplying both sides by the denominator and simplifying, we get:

s^2 + 3s + 1 = A(s + 4 - sqrt(15))(s + 4 + sqrt(15)) + B(s + 2)(s + 4 + sqrt(15)) + C(s + 2)(s + 4 - sqrt(15))

Setting s = -4 + sqrt(15), we get:

-4 + sqrt(15) = A(-4 + sqrt(15) + 4 + sqrt(15))

Solving for A, we get:

A = (-4 + sqrt(15)) / (2sqrt(15))

Setting s = -4 - sqrt(15), we get:

-4 - sqrt(15) = A(-4 - sqrt(15) + 4 + sqrt(15))

Solving for A, we get:

A = (-4 - sqrt(15)) / (-2sqrt(15))

Setting s = -2, we get:

-1 = B(-2)(-2 + 4 + sqrt(15))

Solving for B, we get:

B = (-1) / (2sqrt(15) + 4)

Setting s =