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Límite de la función cot(5*x)/cot(3*x)

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Solución

Ha introducido [src]
     /cot(5*x)\
 lim |--------|
x->0+\cot(3*x)/
$$\lim_{x \to 0^+}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right)$$
Limit(cot(5*x)/cot(3*x), x, 0)
Método de l'Hopital
Tenemos la indeterminación de tipo
0/0,

tal que el límite para el numerador es
$$\lim_{x \to 0^+} \frac{1}{\cot{\left(3 x \right)}} = 0$$
y el límite para el denominador es
$$\lim_{x \to 0^+} \frac{1}{\cot{\left(5 x \right)}} = 0$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to 0^+}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \frac{1}{\cot{\left(3 x \right)}}}{\frac{d}{d x} \frac{1}{\cot{\left(5 x \right)}}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{3 \cot^{2}{\left(3 x \right)} \cot^{2}{\left(5 x \right)} + 3 \cot^{2}{\left(5 x \right)}}{\left(5 \cot^{2}{\left(5 x \right)} + 5\right) \cot^{2}{\left(3 x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \frac{1}{5 \cot^{2}{\left(5 x \right)} + 5}}{\frac{d}{d x} \frac{\cot^{2}{\left(3 x \right)}}{3 \cot^{2}{\left(3 x \right)} \cot^{2}{\left(5 x \right)} + 3 \cot^{2}{\left(5 x \right)}}}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{5 \left(- 10 \cot^{2}{\left(5 x \right)} - 10\right) \cot{\left(5 x \right)}}{\left(\frac{\left(- 6 \cot^{2}{\left(3 x \right)} - 6\right) \cot{\left(3 x \right)}}{3 \cot^{2}{\left(3 x \right)} \cot^{2}{\left(5 x \right)} + 3 \cot^{2}{\left(5 x \right)}} + \frac{\left(- 3 \left(- 6 \cot^{2}{\left(3 x \right)} - 6\right) \cot{\left(3 x \right)} \cot^{2}{\left(5 x \right)} - 3 \left(- 10 \cot^{2}{\left(5 x \right)} - 10\right) \cot^{2}{\left(3 x \right)} \cot{\left(5 x \right)} - 3 \left(- 10 \cot^{2}{\left(5 x \right)} - 10\right) \cot{\left(5 x \right)}\right) \cot^{2}{\left(3 x \right)}}{\left(3 \cot^{2}{\left(3 x \right)} \cot^{2}{\left(5 x \right)} + 3 \cot^{2}{\left(5 x \right)}\right)^{2}}\right) \left(5 \cot^{2}{\left(5 x \right)} + 5\right)^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{5 \left(- 10 \cot^{2}{\left(5 x \right)} - 10\right) \cot{\left(5 x \right)}}{\left(\frac{\left(- 6 \cot^{2}{\left(3 x \right)} - 6\right) \cot{\left(3 x \right)}}{3 \cot^{2}{\left(3 x \right)} \cot^{2}{\left(5 x \right)} + 3 \cot^{2}{\left(5 x \right)}} + \frac{\left(- 3 \left(- 6 \cot^{2}{\left(3 x \right)} - 6\right) \cot{\left(3 x \right)} \cot^{2}{\left(5 x \right)} - 3 \left(- 10 \cot^{2}{\left(5 x \right)} - 10\right) \cot^{2}{\left(3 x \right)} \cot{\left(5 x \right)} - 3 \left(- 10 \cot^{2}{\left(5 x \right)} - 10\right) \cot{\left(5 x \right)}\right) \cot^{2}{\left(3 x \right)}}{\left(3 \cot^{2}{\left(3 x \right)} \cot^{2}{\left(5 x \right)} + 3 \cot^{2}{\left(5 x \right)}\right)^{2}}\right) \left(5 \cot^{2}{\left(5 x \right)} + 5\right)^{2}}\right)$$
=
$$\frac{3}{5}$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 2 vez (veces)
Gráfica
Respuesta rápida [src]
3/5
$$\frac{3}{5}$$
A la izquierda y a la derecha [src]
     /cot(5*x)\
 lim |--------|
x->0+\cot(3*x)/
$$\lim_{x \to 0^+}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right)$$
3/5
$$\frac{3}{5}$$
= 0.6
     /cot(5*x)\
 lim |--------|
x->0-\cot(3*x)/
$$\lim_{x \to 0^-}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right)$$
3/5
$$\frac{3}{5}$$
= 0.6
= 0.6
Otros límites con x→0, -oo, +oo, 1
$$\lim_{x \to 0^-}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right) = \frac{3}{5}$$
Más detalles con x→0 a la izquierda
$$\lim_{x \to 0^+}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right) = \frac{3}{5}$$
$$\lim_{x \to \infty}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right)$$
Más detalles con x→oo
$$\lim_{x \to 1^-}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right) = \frac{\tan{\left(3 \right)}}{\tan{\left(5 \right)}}$$
Más detalles con x→1 a la izquierda
$$\lim_{x \to 1^+}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right) = \frac{\tan{\left(3 \right)}}{\tan{\left(5 \right)}}$$
Más detalles con x→1 a la derecha
$$\lim_{x \to -\infty}\left(\frac{\cot{\left(5 x \right)}}{\cot{\left(3 x \right)}}\right)$$
Más detalles con x→-oo
Respuesta numérica [src]
0.6
0.6