# Need help for Laplace transform

• Dec 15th 2011, 10:33 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, 10:51 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, 11:52 AM
moonnightingale
Re: Need help for Laplace transform
i could not find
• Dec 15th 2011, 04:03 PM
Prove It
Re: Need help for Laplace transform
\displaystyle \displaystyle \begin{align*} \mathcal{L}\left\{e^{at}f(t)\right\} = F(t - a) \end{align*}
• Dec 16th 2011, 01:13 AM
chisigma
Re: Need help for Laplace transform
If the function is $\displaystyle f(t)=e^{- a t}\ u(-t)$ then fot $\displaystyle t>0$ is $\displaystyle f(t)=0$, so that its single side Laplace Tranform is...

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

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Marry Christmas from Serbia

$\displaystyle \chi$ $\displaystyle \sigma$