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f-x-0-x-e-t-t-2-2-dt-show-that-0-1-f-t-dt-e-1-




Question Number 147275 by ArielVyny last updated on 19/Jul/21
f(x)=∫_0 ^x e^(t−(t^2 /2)) dt   show that ∫_0 ^1 f(t)dt=(√e)−1
$${f}\left({x}\right)=\int_{\mathrm{0}} ^{{x}} {e}^{{t}−\frac{{t}^{\mathrm{2}} }{\mathrm{2}}} {dt}\: \\ $$$${show}\:{that}\:\int_{\mathrm{0}} ^{\mathrm{1}} {f}\left({t}\right){dt}=\sqrt{{e}}−\mathrm{1} \\ $$
Answered by mindispower last updated on 19/Jul/21
∫_0 ^1 f(t)dt=[tf(t)]_0 ^1 −∫_0 ^1 tf′(t)dt  =f(1)−∫_0 ^1 te^(t−(t^2 /2)) dt  =∫_0 ^1 (1−t)e^(t−(t^2 /2)) dt=[e^(t−(t^2 /2)) ]_0 ^1 =(√e)−1
$$\int_{\mathrm{0}} ^{\mathrm{1}} {f}\left({t}\right){dt}=\left[{tf}\left({t}\right)\right]_{\mathrm{0}} ^{\mathrm{1}} −\int_{\mathrm{0}} ^{\mathrm{1}} {tf}'\left({t}\right){dt} \\ $$$$={f}\left(\mathrm{1}\right)−\int_{\mathrm{0}} ^{\mathrm{1}} {te}^{{t}−\frac{{t}^{\mathrm{2}} }{\mathrm{2}}} {dt} \\ $$$$=\int_{\mathrm{0}} ^{\mathrm{1}} \left(\mathrm{1}−{t}\right){e}^{{t}−\frac{{t}^{\mathrm{2}} }{\mathrm{2}}} {dt}=\left[{e}^{{t}−\frac{{t}^{\mathrm{2}} }{\mathrm{2}}} \right]_{\mathrm{0}} ^{\mathrm{1}} =\sqrt{{e}}−\mathrm{1} \\ $$
Commented by ArielVyny last updated on 20/Jul/21
thank sir
$${thank}\:{sir} \\ $$

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