Question Number 138552 by mnjuly1970 last updated on 14/Apr/21
$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:...{nice}\:\:\:\:\:\:\:\:{mathemayics}\:... \\ $$$$\:\:\:\:\:\:\:\boldsymbol{\phi}=\int_{\mathrm{0}} ^{\:\infty} \frac{{sin}\left({tan}\left({x}\right)\right)}{{x}}{dx}=\frac{\pi}{\mathrm{2}}\left(\mathrm{1}−\frac{\mathrm{1}}{{e}}\right) \\ $$$$\:\:....... \\ $$