Why do we use laplace transform to solve the integral $\int _{0}^{\infty}\frac{\sin x}{x}dx$ ? why is it insolvable if we go the normal way

calculusdefinite integralsimproper-integralsintuition

We use Laplace Transform to solve $\int _{0}^{\infty}\frac{\sin x}{x}dx$ as shown below:
$\DeclareMathOperator{\arccot}{arccot}$
We use the property $L(\frac{\sin x}{x})=\int _{s}^{\infty}\frac{1}{s^{\prime2}+1}ds^\prime=\frac{\pi}{2}-\arctan(s)=\arccot(s)$.

Now we use the laplace transform definition $\int _{0}^{\infty}e^{-sx}\frac{\sin x}{x}dx=\arccot(s)$
and put $s=0$, getting:

$\int _{0}^{\infty}\frac{\sin x}{x}dx=\arccot(0)=\frac{\pi}{2}$

I would like to know why this is the case (if possible in a intuitive way) and why this function is not solvable (the integration continues indefinitely) using normal (Integration by parts) integration methods.

Edit: The edits are in bold (in the original question).

Edit 2: I thank everyone for your answers and comments. I would request you to put up some visual/graphic representation (if possible) to explain this so that I can have an intuitive understanding. For example, The definite integral gives the area under the curve right ? So what changes when we solve it using Laplace (or other methods) and why is it not possible to find the area of the curve using integration by parts?

Best Answer

By Louville's Thoerem, the sinc function has no elementary anti-derivative and so the improper integral has to be calculated through other methods such as Laplace Transform or through complex analytical methods.

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