Why does laplace trancsform of trigonometric functions like tan,sec , cosec,cot,..and logarithmic functions doesnot exist? what is the reason behind that?

pls help friends...

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- December 26th 2010, 07:20 AMvishnuk5320Laplace transform
Why does laplace trancsform of trigonometric functions like tan,sec , cosec,cot,..and logarithmic functions doesnot exist? what is the reason behind that?

pls help friends... - December 26th 2010, 08:16 AMchisigma
The question has to be proposed in a more precise form!... for example the 'logarithmic function' is perfectly L-transformable...

Kind regards

- December 26th 2010, 08:41 AMchisigma
... in general necerssary condition for the existence of the integral...

(1)

... is that is*locally integrable*on . A function is said to be 'locally integrable' if it is integrable on any compact set of its domain of definition. Functions like , , , etc... are not locally integrable on ...

Kind regards

- December 27th 2010, 01:39 AMvishnuk5320
i mean L(log t).....

- December 27th 2010, 03:10 AMFernandoRevilla
Use the integral expression of the Euler Mascheroni constant:

you'll obtain:

Fernando Revilla - December 27th 2010, 11:55 AMFernandoRevilla
Maybe I missed your initial question:

Perhaps you mean that you don't see some Laplace transformed in the standard tables. The reason is that some of them, don't exist (it has been already commented by**chisigma**). In other cases, (for example, for the logarithmic funcion) we need some previous results.

Fernando Revilla