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Límite de la función (3*sin(x)-3*sin(2*x)/2-x*(-cos(2*x)+cos(x)))/(1-cos(x))^2

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Solución

Ha introducido [src]
     /           3*sin(2*x)                         \
     |3*sin(x) - ---------- - x*(-cos(2*x) + cos(x))|
     |               2                              |
 lim |----------------------------------------------|
x->0+|                            2                 |
     \                (1 - cos(x))                  /
$$\lim_{x \to 0^+}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right)$$
Limit((3*sin(x) - 3*sin(2*x)/2 - x*(-cos(2*x) + cos(x)))/(1 - cos(x))^2, x, 0)
Método de l'Hopital
Tenemos la indeterminación de tipo
0/0,

tal que el límite para el numerador es
$$\lim_{x \to 0^+}\left(- 2 x \cos{\left(x \right)} + 2 x \cos{\left(2 x \right)} + 6 \sin{\left(x \right)} - 3 \sin{\left(2 x \right)}\right) = 0$$
y el límite para el denominador es
$$\lim_{x \to 0^+}\left(2 \cos^{2}{\left(x \right)} - 4 \cos{\left(x \right)} + 2\right) = 0$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to 0^+}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right)$$
=
Introducimos una pequeña modificación de la función bajo el signo del límite
$$\lim_{x \to 0^+}\left(\frac{- 2 x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + 6 \sin{\left(x \right)} - 3 \sin{\left(2 x \right)}}{2 \left(1 - \cos{\left(x \right)}\right)^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(- 2 x \cos{\left(x \right)} + 2 x \cos{\left(2 x \right)} + 6 \sin{\left(x \right)} - 3 \sin{\left(2 x \right)}\right)}{\frac{d}{d x} \left(2 \cos^{2}{\left(x \right)} - 4 \cos{\left(x \right)} + 2\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{2 x \sin{\left(x \right)} - 4 x \sin{\left(2 x \right)} + 4 \cos{\left(x \right)} - 4 \cos{\left(2 x \right)}}{- 4 \sin{\left(x \right)} \cos{\left(x \right)} + 4 \sin{\left(x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(2 x \sin{\left(x \right)} - 4 x \sin{\left(2 x \right)} + 4 \cos{\left(x \right)} - 4 \cos{\left(2 x \right)}\right)}{\frac{d}{d x} \left(- 4 \sin{\left(x \right)} \cos{\left(x \right)} + 4 \sin{\left(x \right)}\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{2 x \cos{\left(x \right)} - 8 x \cos{\left(2 x \right)} - 2 \sin{\left(x \right)} + 4 \sin{\left(2 x \right)}}{4 \sin^{2}{\left(x \right)} - 4 \cos^{2}{\left(x \right)} + 4 \cos{\left(x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(2 x \cos{\left(x \right)} - 8 x \cos{\left(2 x \right)} - 2 \sin{\left(x \right)} + 4 \sin{\left(2 x \right)}\right)}{\frac{d}{d x} \left(4 \sin^{2}{\left(x \right)} - 4 \cos^{2}{\left(x \right)} + 4 \cos{\left(x \right)}\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{- 2 x \sin{\left(x \right)} + 16 x \sin{\left(2 x \right)}}{16 \sin{\left(x \right)} \cos{\left(x \right)} - 4 \sin{\left(x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{- 2 x \sin{\left(x \right)} + 16 x \sin{\left(2 x \right)}}{16 \sin{\left(x \right)} \cos{\left(x \right)} - 4 \sin{\left(x \right)}}\right)$$
=
$$0$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 3 vez (veces)
Gráfica
Otros límites con x→0, -oo, +oo, 1
$$\lim_{x \to 0^-}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right) = 0$$
Más detalles con x→0 a la izquierda
$$\lim_{x \to 0^+}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right) = 0$$
$$\lim_{x \to \infty}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right)$$
Más detalles con x→oo
$$\lim_{x \to 1^-}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right) = - \frac{- 6 \sin{\left(1 \right)} - 2 \cos{\left(2 \right)} + 2 \cos{\left(1 \right)} + 3 \sin{\left(2 \right)}}{- 4 \cos{\left(1 \right)} + 2 \cos^{2}{\left(1 \right)} + 2}$$
Más detalles con x→1 a la izquierda
$$\lim_{x \to 1^+}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right) = - \frac{- 6 \sin{\left(1 \right)} - 2 \cos{\left(2 \right)} + 2 \cos{\left(1 \right)} + 3 \sin{\left(2 \right)}}{- 4 \cos{\left(1 \right)} + 2 \cos^{2}{\left(1 \right)} + 2}$$
Más detalles con x→1 a la derecha
$$\lim_{x \to -\infty}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right)$$
Más detalles con x→-oo
Respuesta rápida [src]
0
$$0$$
A la izquierda y a la derecha [src]
     /           3*sin(2*x)                         \
     |3*sin(x) - ---------- - x*(-cos(2*x) + cos(x))|
     |               2                              |
 lim |----------------------------------------------|
x->0+|                            2                 |
     \                (1 - cos(x))                  /
$$\lim_{x \to 0^+}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right)$$
0
$$0$$
= -1.44937556952754e-32
     /           3*sin(2*x)                         \
     |3*sin(x) - ---------- - x*(-cos(2*x) + cos(x))|
     |               2                              |
 lim |----------------------------------------------|
x->0-|                            2                 |
     \                (1 - cos(x))                  /
$$\lim_{x \to 0^-}\left(\frac{- x \left(\cos{\left(x \right)} - \cos{\left(2 x \right)}\right) + \left(3 \sin{\left(x \right)} - \frac{3 \sin{\left(2 x \right)}}{2}\right)}{\left(1 - \cos{\left(x \right)}\right)^{2}}\right)$$
0
$$0$$
= 1.44937556952754e-32
= 1.44937556952754e-32
Respuesta numérica [src]
-1.44937556952754e-32
-1.44937556952754e-32