Question Number 66293 by Rio Michael last updated on 12/Aug/19
$${What}\:{do}\:{we}\:{mean}\:{by}\:\: \\ $$$$\:\:\int_{−\infty} ^{+\infty} {f}\left({x}\right)\:{dx}? \\ $$
Commented by mathmax by abdo last updated on 12/Aug/19
$$\int_{−\infty} ^{+\infty} {f}\left({x}\right){dx}\:={lim}_{\xi\rightarrow+\infty} \:\:\int_{−\xi} ^{\xi} {f}\left({x}\right){dx}\:\:{and}\:\int_{−\xi} ^{\xi} {f}\left({x}\right){dx}\:{is}\:{the}\:{surface} \\ $$$${limiteted}\:{by}\:{y}=\mathrm{0}\left(\:\:\left({x}^{'} {ox}\right)\right)\:{and}\:{y}={f}\left({x}\right) \\ $$
Commented by mathmax by abdo last updated on 12/Aug/19
![on]−ξ,ξ[...](Q66297.png)
$$\left.{on}\right]−\xi,\xi\left[...\right. \\ $$
Commented by Rio Michael last updated on 13/Aug/19
$${thanks} \\ $$