# Need help for Laplace transform

• Dec 15th 2011, 11:33 AM
moonnightingale
Need help for Laplace transform
What is laplace transform of
exp(-at)u(-t)

and if laplace of x(t) is 1/s then laplace of dx(t)/dt will be...
• Dec 15th 2011, 11:51 AM
liquidFuzz
Re: Need help for Laplace transform
The first one looks like a frequency shift. The other one like differentiation. Both transforms can be look upon as trivial, so look them up in a table.
• Dec 15th 2011, 12:52 PM
moonnightingale
Re: Need help for Laplace transform
i could not find
• Dec 15th 2011, 05:03 PM
Prove It
Re: Need help for Laplace transform
\displaystyle \begin{align*} \mathcal{L}\left\{e^{at}f(t)\right\} = F(t - a) \end{align*}
• Dec 16th 2011, 02:13 AM
chisigma
Re: Need help for Laplace transform
If the function is $f(t)=e^{- a t}\ u(-t)$ then fot $t>0$ is $f(t)=0$, so that its single side Laplace Tranform is...

$\int_{0}^{+ \infty} f(t)\ e^{- s t} dt =0$

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Marry Christmas from Serbia

$\chi$ $\sigma$