Finding the inverse Laplace transform of ln(1+(1)/(s^2))

Kayden Mills

Kayden Mills

Answered question

2022-11-17

Finding the inverse Laplace transform of ln ( 1 + 1 s 2 )

Answer & Explanation

Jaydon Roth

Jaydon Roth

Beginner2022-11-18Added 13 answers

We can write
ln ( 1 + 1 s 2 ) = ln ( s + i ) + ln ( s i ) 2 ln ( s ) = ( s + i ) ln ( s + i ) + γ s + i + ( s i ) ln ( s i ) + γ s i 2 s ln ( s ) + γ s
We know that
L ( ln ( t ) u ( t ) ) = ln ( s ) + γ s
Therefore
L ( D ( ln ( t ) u ( t ) ) ) = s ln ( s ) + γ s
where D is derivative and
L ( e ± i t D ( ln ( t ) u ( t ) ) ) = ( s ± i ) ln ( s ± i ) + γ s ± i
Now you can complete it.
kemecryncqe9

kemecryncqe9

Beginner2022-11-19Added 6 answers

Since L 1 { s n } = 1 ( n 1 ) ! t n 1 , we have, in wiev of the expansion ln ( 1 x ) = n = 1 x n n :
L 1 { ln ( 1 + 1 s 2 ) } = n = 1 ( 1 ) n n L 1 { s 2 n } = n = 1 ( 1 ) n n t 2 n 1 ( 2 n 1 ) ! .
The last sum can be arranged:
n = 1 ( 1 ) n n t 2 n 1 ( 2 n 1 ) ! = 2 n = 1 ( 1 ) n t 2 n 1 ( 2 n ) ! = 2 t 2 t n = 0 ( 1 ) n t 2 n ( 2 n ) ! = 2 t ( 1 cos t ) .
Thus proving the formula.

Do you have a similar question?

Recalculate according to your conditions!

New Questions in Differential Equations

Ask your question.
Get an expert answer.

Let our experts help you. Answer in as fast as 15 minutes.

Didn't find what you were looking for?