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Question Number 161020 by SANOGO last updated on 10/Dec/21
etudier la convergence  ∫_0 ^(+oo) (1/( (√(x(1+x^2 )))))dx
$${etudier}\:{la}\:{convergence} \\ $$$$\int_{\mathrm{0}} ^{+{oo}} \frac{\mathrm{1}}{\:\sqrt{{x}\left(\mathrm{1}+{x}^{\mathrm{2}} \right)}}{dx} \\ $$
Answered by Ar Brandon last updated on 10/Dec/21
I=∫_0 ^∞ (1/( (√(x(1+x^2 )))))dx=(1/2)∫_0 ^∞ (u^(−(3/4)) /( (√(1+u))))du     =(1/2)β((1/4), (1/4))=(1/( 2(√π)))Γ^2 ((1/4))
$${I}=\int_{\mathrm{0}} ^{\infty} \frac{\mathrm{1}}{\:\sqrt{{x}\left(\mathrm{1}+{x}^{\mathrm{2}} \right)}}{dx}=\frac{\mathrm{1}}{\mathrm{2}}\int_{\mathrm{0}} ^{\infty} \frac{{u}^{−\frac{\mathrm{3}}{\mathrm{4}}} }{\:\sqrt{\mathrm{1}+{u}}}{du} \\ $$$$\:\:\:=\frac{\mathrm{1}}{\mathrm{2}}\beta\left(\frac{\mathrm{1}}{\mathrm{4}},\:\frac{\mathrm{1}}{\mathrm{4}}\right)=\frac{\mathrm{1}}{\:\mathrm{2}\sqrt{\pi}}\Gamma^{\mathrm{2}} \left(\frac{\mathrm{1}}{\mathrm{4}}\right) \\ $$
Commented by SANOGO last updated on 11/Dec/21
merci bien
$${merci}\:{bien} \\ $$

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