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Límite de la función cos(pi*sin(pi*x/2)/2)/sin(pi^2*(1-x)*tan(pi*x/2))

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Solución

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

tal que el límite para el numerador es
$$\lim_{x \to 1^+} \cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)} = 0$$
y el límite para el denominador es
$$\lim_{x \to 1^+} \sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)} = 0$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to 1^+}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
=
Introducimos una pequeña modificación de la función bajo el signo del límite
$$\lim_{x \to 1^+}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
=
$$\lim_{x \to 1^+}\left(\frac{\frac{d}{d x} \cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\frac{d}{d x} \sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
=
$$\lim_{x \to 1^+}\left(- \frac{\pi^{2} \sin{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)} \cos{\left(\frac{\pi x}{2} \right)}}{4 \left(\frac{\pi^{3} \left(1 - x\right) \left(\tan^{2}{\left(\frac{\pi x}{2} \right)} + 1\right)}{2} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)}\right) \cos{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
=
$$\lim_{x \to 1^+}\left(- \frac{\pi^{2} \cos{\left(\frac{\pi x}{2} \right)}}{4 \left(\frac{\pi^{3} \left(1 - x\right) \left(\tan^{2}{\left(\frac{\pi x}{2} \right)} + 1\right)}{2} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)}\right)}\right)$$
=
$$\lim_{x \to 1^+}\left(\frac{\frac{d}{d x} \left(- \frac{\pi^{2} \cos{\left(\frac{\pi x}{2} \right)}}{4}\right)}{\frac{d}{d x} \left(\frac{\pi^{3} \left(1 - x\right) \left(\tan^{2}{\left(\frac{\pi x}{2} \right)} + 1\right)}{2} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)}\right)}\right)$$
=
$$\lim_{x \to 1^+}\left(\frac{\pi^{3} \sin{\left(\frac{\pi x}{2} \right)}}{8 \left(\frac{\pi^{4} \left(1 - x\right) \left(\tan^{2}{\left(\frac{\pi x}{2} \right)} + 1\right) \tan{\left(\frac{\pi x}{2} \right)}}{2} - \pi^{3} \left(\tan^{2}{\left(\frac{\pi x}{2} \right)} + 1\right)\right)}\right)$$
=
$$\lim_{x \to 1^+}\left(\frac{\pi^{3}}{8 \left(- \frac{\pi^{4} x \tan^{3}{\left(\frac{\pi x}{2} \right)}}{2} - \frac{\pi^{4} x \tan{\left(\frac{\pi x}{2} \right)}}{2} + \frac{\pi^{4} \tan^{3}{\left(\frac{\pi x}{2} \right)}}{2} - \pi^{3} \tan^{2}{\left(\frac{\pi x}{2} \right)} + \frac{\pi^{4} \tan{\left(\frac{\pi x}{2} \right)}}{2} - \pi^{3}\right)}\right)$$
=
$$\lim_{x \to 1^+}\left(\frac{\pi^{3}}{8 \left(- \frac{\pi^{4} x \tan^{3}{\left(\frac{\pi x}{2} \right)}}{2} - \frac{\pi^{4} x \tan{\left(\frac{\pi x}{2} \right)}}{2} + \frac{\pi^{4} \tan^{3}{\left(\frac{\pi x}{2} \right)}}{2} - \pi^{3} \tan^{2}{\left(\frac{\pi x}{2} \right)} + \frac{\pi^{4} \tan{\left(\frac{\pi x}{2} \right)}}{2} - \pi^{3}\right)}\right)$$
=
$$\lim_{x \to 1^+}\left(- \frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} x \tan{\left(\frac{\pi x}{2} \right)} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 2 vez (veces)
Gráfica
Otros límites con x→0, -oo, +oo, 1
$$\lim_{x \to 1^-}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right) = \lim_{x \to 1^+}\left(- \frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} x \tan{\left(\frac{\pi x}{2} \right)} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
Más detalles con x→1 a la izquierda
$$\lim_{x \to 1^+}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right) = \lim_{x \to 1^+}\left(- \frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} x \tan{\left(\frac{\pi x}{2} \right)} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
$$\lim_{x \to \infty}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
Más detalles con x→oo
$$\lim_{x \to 0^-}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right) = -\infty$$
Más detalles con x→0 a la izquierda
$$\lim_{x \to 0^+}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right) = \infty$$
Más detalles con x→0 a la derecha
$$\lim_{x \to -\infty}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
Más detalles con x→-oo
Respuesta rápida [src]
     /             /      /pi*x\\           \
     |             |pi*sin|----||           |
     |             |      \ 2  /|           |
     |         -cos|------------|           |
     |             \     2      /           |
 lim |--------------------------------------|
x->1+|   /    2    /pi*x\       2    /pi*x\\|
     |sin|- pi *tan|----| + x*pi *tan|----|||
     \   \         \ 2  /            \ 2  ///
$$\lim_{x \to 1^+}\left(- \frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} x \tan{\left(\frac{\pi x}{2} \right)} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
A la izquierda y a la derecha [src]
     /       /      /pi*x\\     \
     |       |pi*sin|----||     |
     |       |      \ 2  /|     |
     |    cos|------------|     |
     |       \     2      /     |
 lim |--------------------------|
x->1+|   /  2            /pi*x\\|
     |sin|pi *(1 - x)*tan|----|||
     \   \               \ 2  ///
$$\lim_{x \to 1^+}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
     /             /      /pi*x\\           \
     |             |pi*sin|----||           |
     |             |      \ 2  /|           |
     |         -cos|------------|           |
     |             \     2      /           |
 lim |--------------------------------------|
x->1+|   /    2    /pi*x\       2    /pi*x\\|
     |sin|- pi *tan|----| + x*pi *tan|----|||
     \   \         \ 2  /            \ 2  ///
$$\lim_{x \to 1^+}\left(- \frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} x \tan{\left(\frac{\pi x}{2} \right)} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
= -0.375
     /       /      /pi*x\\     \
     |       |pi*sin|----||     |
     |       |      \ 2  /|     |
     |    cos|------------|     |
     |       \     2      /     |
 lim |--------------------------|
x->1-|   /  2            /pi*x\\|
     |sin|pi *(1 - x)*tan|----|||
     \   \               \ 2  ///
$$\lim_{x \to 1^-}\left(\frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} \left(1 - x\right) \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
     /             /      /pi*x\\           \
     |             |pi*sin|----||           |
     |             |      \ 2  /|           |
     |         -cos|------------|           |
     |             \     2      /           |
 lim |--------------------------------------|
x->1-|   /    2    /pi*x\       2    /pi*x\\|
     |sin|- pi *tan|----| + x*pi *tan|----|||
     \   \         \ 2  /            \ 2  ///
$$\lim_{x \to 1^-}\left(- \frac{\cos{\left(\frac{\pi \sin{\left(\frac{\pi x}{2} \right)}}{2} \right)}}{\sin{\left(\pi^{2} x \tan{\left(\frac{\pi x}{2} \right)} - \pi^{2} \tan{\left(\frac{\pi x}{2} \right)} \right)}}\right)$$
= -0.375
= -0.375
Respuesta numérica [src]
-0.375
-0.375