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Límite de la función log(1+tan(2*x))^2/(log(10)^2*sin(5*x)^2)

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Solución

Ha introducido [src]
     /   2              \
     |log (1 + tan(2*x))|
 lim |------------------|
x->0+|   2        2     |
     \log (10)*sin (5*x)/
$$\lim_{x \to 0^+}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
Limit(log(1 + tan(2*x))^2/((log(10)^2*sin(5*x)^2)), x, 0)
Método de l'Hopital
Tenemos la indeterminación de tipo
0/0,

tal que el límite para el numerador es
$$\lim_{x \to 0^+} \log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2} = 0$$
y el límite para el denominador es
$$\lim_{x \to 0^+}\left(\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}\right) = 0$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to 0^+}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
=
Introducimos una pequeña modificación de la función bajo el signo del límite
$$\lim_{x \to 0^+}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\frac{d}{d x} \log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\left(2 \tan^{2}{\left(2 x \right)} + 2\right) \log{\left(\tan{\left(2 x \right)} + 1 \right)}}{5 \left(\tan{\left(2 x \right)} + 1\right) \log{\left(10 \right)}^{2} \sin{\left(5 x \right)} \cos{\left(5 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{2 \log{\left(\tan{\left(2 x \right)} + 1 \right)}}{5 \log{\left(10 \right)}^{2} \sin{\left(5 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \log{\left(\tan{\left(2 x \right)} + 1 \right)}}{\frac{d}{d x} \frac{5 \log{\left(10 \right)}^{2} \sin{\left(5 x \right)}}{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{2 \left(2 \tan^{2}{\left(2 x \right)} + 2\right)}{25 \left(\tan{\left(2 x \right)} + 1\right) \log{\left(10 \right)}^{2} \cos{\left(5 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{4}{25 \log{\left(10 \right)}^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{4}{25 \log{\left(10 \right)}^{2}}\right)$$
=
$$\frac{4}{25 \log{\left(10 \right)}^{2}}$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 2 vez (veces)
Gráfica
Respuesta rápida [src]
     4     
-----------
      2    
25*log (10)
$$\frac{4}{25 \log{\left(10 \right)}^{2}}$$
A la izquierda y a la derecha [src]
     /   2              \
     |log (1 + tan(2*x))|
 lim |------------------|
x->0+|   2        2     |
     \log (10)*sin (5*x)/
$$\lim_{x \to 0^+}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
     4     
-----------
      2    
25*log (10)
$$\frac{4}{25 \log{\left(10 \right)}^{2}}$$
= 0.0301778715218582
     /   2              \
     |log (1 + tan(2*x))|
 lim |------------------|
x->0-|   2        2     |
     \log (10)*sin (5*x)/
$$\lim_{x \to 0^-}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
     4     
-----------
      2    
25*log (10)
$$\frac{4}{25 \log{\left(10 \right)}^{2}}$$
= 0.0301778715218582
= 0.0301778715218582
Otros límites con x→0, -oo, +oo, 1
$$\lim_{x \to 0^-}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right) = \frac{4}{25 \log{\left(10 \right)}^{2}}$$
Más detalles con x→0 a la izquierda
$$\lim_{x \to 0^+}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right) = \frac{4}{25 \log{\left(10 \right)}^{2}}$$
$$\lim_{x \to \infty}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
Más detalles con x→oo
$$\lim_{x \to 1^-}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right) = \frac{- \pi^{2} + \log{\left(-1 - \tan{\left(2 \right)} \right)}^{2} + 2 i \pi \log{\left(-1 - \tan{\left(2 \right)} \right)}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 \right)}}$$
Más detalles con x→1 a la izquierda
$$\lim_{x \to 1^+}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right) = \frac{- \pi^{2} + \log{\left(-1 - \tan{\left(2 \right)} \right)}^{2} + 2 i \pi \log{\left(-1 - \tan{\left(2 \right)} \right)}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 \right)}}$$
Más detalles con x→1 a la derecha
$$\lim_{x \to -\infty}\left(\frac{\log{\left(\tan{\left(2 x \right)} + 1 \right)}^{2}}{\log{\left(10 \right)}^{2} \sin^{2}{\left(5 x \right)}}\right)$$
Más detalles con x→-oo
Respuesta numérica [src]
0.0301778715218582
0.0301778715218582