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x*log(2*atan(x)/pi)

Límite de la función x*log(2*atan(x)/pi)

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Solución

Ha introducido [src]
     /     /2*atan(x)\\
 lim |x*log|---------||
x->oo\     \    pi   //
limx(xlog(2atan(x)π))\lim_{x \to \infty}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right)
Limit(x*log((2*atan(x))/pi), x, oo, dir='-')
Método de l'Hopital
Tenemos la indeterminación de tipo
oo/-oo,

tal que el límite para el numerador es
limxx=\lim_{x \to \infty} x = \infty
y el límite para el denominador es
limx1log(2atan(x)π)=\lim_{x \to \infty} \frac{1}{\log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}} = -\infty
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
limx(xlog(2atan(x)π))\lim_{x \to \infty}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right)
=
Introducimos una pequeña modificación de la función bajo el signo del límite
limx(xlog(2atan(x)π))\lim_{x \to \infty}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right)
=
limx(ddxxddx1log(2atan(x)π))\lim_{x \to \infty}\left(\frac{\frac{d}{d x} x}{\frac{d}{d x} \frac{1}{\log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}}}\right)
=
limx((x2+1)log(2atan(x)π)2atan(x))\lim_{x \to \infty}\left(- \left(x^{2} + 1\right) \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}^{2} \operatorname{atan}{\left(x \right)}\right)
=
limx(π(x2+1)log(2atan(x)π)22)\lim_{x \to \infty}\left(- \frac{\pi \left(x^{2} + 1\right) \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}^{2}}{2}\right)
=
limx(ddx(π(x2+1)2)ddx1log(2atan(x)π)2)\lim_{x \to \infty}\left(\frac{\frac{d}{d x} \left(- \frac{\pi \left(x^{2} + 1\right)}{2}\right)}{\frac{d}{d x} \frac{1}{\log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}^{2}}}\right)
=
limx(πx(x2+1)log(2atan(x)π)3atan(x)2)\lim_{x \to \infty}\left(\frac{\pi x \left(x^{2} + 1\right) \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}^{3} \operatorname{atan}{\left(x \right)}}{2}\right)
=
limx(π2x(x2+1)log(2atan(x)π)34)\lim_{x \to \infty}\left(\frac{\pi^{2} x \left(x^{2} + 1\right) \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}^{3}}{4}\right)
=
limx(ddxπ2x(x2+1)4ddx1log(2atan(x)π)3)\lim_{x \to \infty}\left(\frac{\frac{d}{d x} \frac{\pi^{2} x \left(x^{2} + 1\right)}{4}}{\frac{d}{d x} \frac{1}{\log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}^{3}}}\right)
=
limx((x2+1)(π2x22+π2(x2+1)4)log(2atan(x)π)4atan(x)3)\lim_{x \to \infty}\left(- \frac{\left(x^{2} + 1\right) \left(\frac{\pi^{2} x^{2}}{2} + \frac{\pi^{2} \left(x^{2} + 1\right)}{4}\right) \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}^{4} \operatorname{atan}{\left(x \right)}}{3}\right)
=
limx((3π2x24+π24)(πx2log(atan(x))462πx2log(2)log(atan(x))33+2πx2log(π)log(atan(x))33πx2log(π)2log(atan(x))2πx2log(2)2log(atan(x))2+2πx2log(2)log(π)log(atan(x))22πx2log(2)log(π)2log(atan(x))2πx2log(2)3log(atan(x))3+2πx2log(π)3log(atan(x))3+2πx2log(2)2log(π)log(atan(x))πx2log(2)2log(π)2πx2log(π)46πx2log(2)46+2πx2log(2)3log(π)3+2πx2log(2)log(π)33πlog(atan(x))462πlog(2)log(atan(x))33+2πlog(π)log(atan(x))33πlog(π)2log(atan(x))2πlog(2)2log(atan(x))2+2πlog(2)log(π)log(atan(x))22πlog(2)log(π)2log(atan(x))2πlog(2)3log(atan(x))3+2πlog(π)3log(atan(x))3+2πlog(2)2log(π)log(atan(x))πlog(2)2log(π)2πlog(π)46πlog(2)46+2πlog(2)3log(π)3+2πlog(2)log(π)33))\lim_{x \to \infty}\left(\left(\frac{3 \pi^{2} x^{2}}{4} + \frac{\pi^{2}}{4}\right) \left(- \frac{\pi x^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{4}}{6} - \frac{2 \pi x^{2} \log{\left(2 \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} + \frac{2 \pi x^{2} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} - \pi x^{2} \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - \pi x^{2} \log{\left(2 \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} + 2 \pi x^{2} \log{\left(2 \right)} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - 2 \pi x^{2} \log{\left(2 \right)} \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \frac{2 \pi x^{2} \log{\left(2 \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + \frac{2 \pi x^{2} \log{\left(\pi \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + 2 \pi x^{2} \log{\left(2 \right)}^{2} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \pi x^{2} \log{\left(2 \right)}^{2} \log{\left(\pi \right)}^{2} - \frac{\pi x^{2} \log{\left(\pi \right)}^{4}}{6} - \frac{\pi x^{2} \log{\left(2 \right)}^{4}}{6} + \frac{2 \pi x^{2} \log{\left(2 \right)}^{3} \log{\left(\pi \right)}}{3} + \frac{2 \pi x^{2} \log{\left(2 \right)} \log{\left(\pi \right)}^{3}}{3} - \frac{\pi \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{4}}{6} - \frac{2 \pi \log{\left(2 \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} + \frac{2 \pi \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} - \pi \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - \pi \log{\left(2 \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} + 2 \pi \log{\left(2 \right)} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - 2 \pi \log{\left(2 \right)} \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \frac{2 \pi \log{\left(2 \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + \frac{2 \pi \log{\left(\pi \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + 2 \pi \log{\left(2 \right)}^{2} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \pi \log{\left(2 \right)}^{2} \log{\left(\pi \right)}^{2} - \frac{\pi \log{\left(\pi \right)}^{4}}{6} - \frac{\pi \log{\left(2 \right)}^{4}}{6} + \frac{2 \pi \log{\left(2 \right)}^{3} \log{\left(\pi \right)}}{3} + \frac{2 \pi \log{\left(2 \right)} \log{\left(\pi \right)}^{3}}{3}\right)\right)
=
limx((3π2x24+π24)(πx2log(atan(x))462πx2log(2)log(atan(x))33+2πx2log(π)log(atan(x))33πx2log(π)2log(atan(x))2πx2log(2)2log(atan(x))2+2πx2log(2)log(π)log(atan(x))22πx2log(2)log(π)2log(atan(x))2πx2log(2)3log(atan(x))3+2πx2log(π)3log(atan(x))3+2πx2log(2)2log(π)log(atan(x))πx2log(2)2log(π)2πx2log(π)46πx2log(2)46+2πx2log(2)3log(π)3+2πx2log(2)log(π)33πlog(atan(x))462πlog(2)log(atan(x))33+2πlog(π)log(atan(x))33πlog(π)2log(atan(x))2πlog(2)2log(atan(x))2+2πlog(2)log(π)log(atan(x))22πlog(2)log(π)2log(atan(x))2πlog(2)3log(atan(x))3+2πlog(π)3log(atan(x))3+2πlog(2)2log(π)log(atan(x))πlog(2)2log(π)2πlog(π)46πlog(2)46+2πlog(2)3log(π)3+2πlog(2)log(π)33))\lim_{x \to \infty}\left(\left(\frac{3 \pi^{2} x^{2}}{4} + \frac{\pi^{2}}{4}\right) \left(- \frac{\pi x^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{4}}{6} - \frac{2 \pi x^{2} \log{\left(2 \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} + \frac{2 \pi x^{2} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} - \pi x^{2} \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - \pi x^{2} \log{\left(2 \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} + 2 \pi x^{2} \log{\left(2 \right)} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - 2 \pi x^{2} \log{\left(2 \right)} \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \frac{2 \pi x^{2} \log{\left(2 \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + \frac{2 \pi x^{2} \log{\left(\pi \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + 2 \pi x^{2} \log{\left(2 \right)}^{2} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \pi x^{2} \log{\left(2 \right)}^{2} \log{\left(\pi \right)}^{2} - \frac{\pi x^{2} \log{\left(\pi \right)}^{4}}{6} - \frac{\pi x^{2} \log{\left(2 \right)}^{4}}{6} + \frac{2 \pi x^{2} \log{\left(2 \right)}^{3} \log{\left(\pi \right)}}{3} + \frac{2 \pi x^{2} \log{\left(2 \right)} \log{\left(\pi \right)}^{3}}{3} - \frac{\pi \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{4}}{6} - \frac{2 \pi \log{\left(2 \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} + \frac{2 \pi \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{3}}{3} - \pi \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - \pi \log{\left(2 \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} + 2 \pi \log{\left(2 \right)} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)}^{2} - 2 \pi \log{\left(2 \right)} \log{\left(\pi \right)}^{2} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \frac{2 \pi \log{\left(2 \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + \frac{2 \pi \log{\left(\pi \right)}^{3} \log{\left(\operatorname{atan}{\left(x \right)} \right)}}{3} + 2 \pi \log{\left(2 \right)}^{2} \log{\left(\pi \right)} \log{\left(\operatorname{atan}{\left(x \right)} \right)} - \pi \log{\left(2 \right)}^{2} \log{\left(\pi \right)}^{2} - \frac{\pi \log{\left(\pi \right)}^{4}}{6} - \frac{\pi \log{\left(2 \right)}^{4}}{6} + \frac{2 \pi \log{\left(2 \right)}^{3} \log{\left(\pi \right)}}{3} + \frac{2 \pi \log{\left(2 \right)} \log{\left(\pi \right)}^{3}}{3}\right)\right)
=
2π- \frac{2}{\pi}
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 3 vez (veces)
Gráfica
02468-8-6-4-2-1010-1.00.0
Otros límites con x→0, -oo, +oo, 1
limx(xlog(2atan(x)π))=2π\lim_{x \to \infty}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right) = - \frac{2}{\pi}
limx0(xlog(2atan(x)π))=0\lim_{x \to 0^-}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right) = 0
Más detalles con x→0 a la izquierda
limx0+(xlog(2atan(x)π))=0\lim_{x \to 0^+}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right) = 0
Más detalles con x→0 a la derecha
limx1(xlog(2atan(x)π))=log(2)\lim_{x \to 1^-}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right) = - \log{\left(2 \right)}
Más detalles con x→1 a la izquierda
limx1+(xlog(2atan(x)π))=log(2)\lim_{x \to 1^+}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right) = - \log{\left(2 \right)}
Más detalles con x→1 a la derecha
limx(xlog(2atan(x)π))=i\lim_{x \to -\infty}\left(x \log{\left(\frac{2 \operatorname{atan}{\left(x \right)}}{\pi} \right)}\right) = - \infty i
Más detalles con x→-oo
Respuesta rápida [src]
-2 
---
 pi
2π- \frac{2}{\pi}
Gráfico
Límite de la función x*log(2*atan(x)/pi)