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Question Number 146933 by mnjuly1970 last updated on 16/Jul/21

                     .....# advanced  calculu#......                  I := ∫_(−∞) ^( +∞) sin(cosh(x).cos(sinhx))dx=?       ....solution ....         I:=(1/2) ∫_(−∞) ^( +∞) {sin (cosh(x)+sinh(x))+sin(cosh(x)−sinh (x))}           :=_(sinh(x)=((e^( x) −e^( −x) )/2)) ^(cosh(x)=((e^( x) +e^( −x) )/2))   (1/2) ∫_(−∞) ^( +∞) {sin(e^x )+sin (e^( −x) )}dx           :=  (1/2) ∫_(−∞) ^( ∞) sin(e^( x) )dx +[(1/2)∫_(−∞) ^( +∞) sin(e^( x) )dx ::  x=^(sub) −x]          := ∫_(−∞) ^( +∞) sin(e^( x)  ) dx =^(e^( x) =y)  ∫_0 ^( ∞) ((sin(t))/t) dt                               ...... I:= (π/2) .....                                  ...m.n.1970...

$$ \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:.....#\:{advanced}\:\:{calculu}#...... \\ $$$$\: \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\mathrm{I}\::=\:\int_{−\infty} ^{\:+\infty} {sin}\left({cosh}\left({x}\right).{cos}\left({sinhx}\right)\right){dx}=? \\ $$$$\:\:\:\:\:....{solution}\:.... \\ $$$$\:\:\:\:\:\:\:\mathrm{I}:=\frac{\mathrm{1}}{\mathrm{2}}\:\int_{−\infty} ^{\:+\infty} \left\{{sin}\:\left({cosh}\left({x}\right)+{sinh}\left({x}\right)\right)+{sin}\left({cosh}\left({x}\right)−{sinh}\:\left({x}\right)\right)\right\} \\ $$$$\:\:\:\:\:\:\:\:\::\underset{{sinh}\left({x}\right)=\frac{{e}^{\:{x}} −{e}^{\:−{x}} }{\mathrm{2}}} {\overset{{cosh}\left({x}\right)=\frac{{e}^{\:{x}} +{e}^{\:−{x}} }{\mathrm{2}}} {=}}\:\:\frac{\mathrm{1}}{\mathrm{2}}\:\int_{−\infty} ^{\:+\infty} \left\{{sin}\left({e}^{{x}} \right)+{sin}\:\left({e}^{\:−{x}} \right)\right\}{dx} \\ $$$$\:\:\:\:\:\:\:\:\::=\:\:\frac{\mathrm{1}}{\mathrm{2}}\:\int_{−\infty} ^{\:\infty} {sin}\left({e}^{\:{x}} \right){dx}\:+\left[\frac{\mathrm{1}}{\mathrm{2}}\int_{−\infty} ^{\:+\infty} {sin}\left({e}^{\:{x}} \right){dx}\:::\:\:{x}\overset{{sub}} {=}−{x}\right] \\ $$$$\:\:\:\:\:\:\:\::=\:\int_{−\infty} ^{\:+\infty} {sin}\left({e}^{\:{x}} \:\right)\:{dx}\:\overset{{e}^{\:{x}} ={y}} {=}\:\int_{\mathrm{0}} ^{\:\infty} \frac{{sin}\left({t}\right)}{{t}}\:{dt}\: \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:......\:\mathrm{I}:=\:\frac{\pi}{\mathrm{2}}\:..... \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:...{m}.{n}.\mathrm{1970}... \\ $$$$\: \\ $$$$ \\ $$

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