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Evaluate-sin-x-dx-




Question Number 31951 by NECx last updated on 17/Mar/18
Evaluate ∫sin (√x)dx
$${Evaluate}\:\int\mathrm{sin}\:\sqrt{{x}}{dx} \\ $$
Answered by mrW2 last updated on 17/Mar/18
u=(√x)  du=(dx/(2(√x)))=(dx/(2u))  dx=2udu  ∫sin (√x)dx  =∫2u sin u du  =−2∫ud cos u  =−2[u cos u−∫cos u du]  =−2[u cos u−sin u]+C  =2[sin u−u cos u]+C  =2[sin (√x)−(√x) cos (√x)]+C
$${u}=\sqrt{{x}} \\ $$$${du}=\frac{{dx}}{\mathrm{2}\sqrt{{x}}}=\frac{{dx}}{\mathrm{2}{u}} \\ $$$${dx}=\mathrm{2}{udu} \\ $$$$\int\mathrm{sin}\:\sqrt{{x}}{dx} \\ $$$$=\int\mathrm{2}{u}\:\mathrm{sin}\:{u}\:{du} \\ $$$$=−\mathrm{2}\int{ud}\:\mathrm{cos}\:{u} \\ $$$$=−\mathrm{2}\left[{u}\:\mathrm{cos}\:{u}−\int\mathrm{cos}\:{u}\:{du}\right] \\ $$$$=−\mathrm{2}\left[{u}\:\mathrm{cos}\:{u}−\mathrm{sin}\:{u}\right]+{C} \\ $$$$=\mathrm{2}\left[\mathrm{sin}\:{u}−{u}\:\mathrm{cos}\:{u}\right]+{C} \\ $$$$=\mathrm{2}\left[\mathrm{sin}\:\sqrt{{x}}−\sqrt{{x}}\:\mathrm{cos}\:\sqrt{{x}}\right]+{C} \\ $$
Commented by mondodotto@gmail.com last updated on 19/Mar/18
thank you very much
$$\mathrm{thank}\:\mathrm{you}\:\mathrm{very}\:\mathrm{much} \\ $$
Commented by NECx last updated on 20/Mar/18
thanks so much!
$${thanks}\:{so}\:{much}! \\ $$

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