How to prove the formula for L{tf(t)}?

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The discussion centers on proving the formula for the Laplace transform of tf(t), specifically that L{tf(t)} equals -dF(s)/ds, where F(s) is the Laplace transform of f(t). The integral definition of L{tf(t)} is provided as ∫₀^∞ tf(t)e^(-st) dt. Participants express difficulty with integration by parts and suggest using the Leibniz integral rule to differentiate under the integral sign. There is a request for clarification on the Leibniz integral rule, indicating the need for a more general approach to handle infinite regions. The conversation highlights the complexities involved in proving this Laplace transform property.
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Homework Statement


L{tf(t)} denotes the Laplace transform of tf(t). I know that it's equal to -dF(s)/ds (where F(s)=L{f(t)}) from a Laplace transform table but I don't know how to prove that.
 
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What is the definition of L{tf(t)}??
 
micromass said:
What is the definition of L{tf(t)}??

\int^\infty_{0} tf(t)e^{-st} dt

I've tried integration by parts, but it didn't help.
 
OK, so I think it's best to start with

F(s)=\int_0^\infty{f(t)e^{-ts}dt}

Now we wish to find F^\prime (s). Do you know Leibniz integral rule??
 
micromass said:
OK, so I think it's best to start with

F(s)=\int_0^\infty{f(t)e^{-ts}dt}

Now we wish to find F^\prime (s). Do you know Leibniz integral rule??

No. state the rule please.
 
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