Find example of a function f such that lim_(t -> x_n) f(t)=oo for infinitely many points x_n and for which the Laplace transform ccL(f) exists.

faois3nh

faois3nh

Answered question

2022-10-13

I am looking for an example of a function f such that lim t x n f ( t ) = for infinitely many points x n and for which the Laplace transform L ( f ) exists.

Answer & Explanation

amilazamiyn

amilazamiyn

Beginner2022-10-14Added 14 answers

Try f : ( 0 , + ) ( 0 , + ) with period 1 and such that, for every 0 < x < 1
f ( x ) = 1 x ( 1 x ) .
Then f ( x ) + when x n, for every nonnegative integer n and, for every λ > 0
L ( f ) ( λ ) = 0 + e λ x f ( x ) d x = 0 1 e λ x f ( x ) d x n 0 e λ n ,
hence
L ( f ) ( λ ) = 1 1 e λ 0 1 e λ x x ( 1 x ) d x ,
and the last integral converges for every λ hence L ( f ) ( λ ) converges.

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