Tenemos la indeterminación de tipo
0/0,
tal que el límite para el numerador es
$$\lim_{x \to 0^+}\left(\frac{x \left(1 - x\right) \left(x + 1\right)^{2} \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}}\right) = 0$$
y el límite para el denominador es
$$\lim_{x \to 0^+}\left(\cos{\left(x \right)} - 1\right) = 0$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to 0^+}\left(\frac{x \left(x + 1\right)^{2} \left(1 - x\right) \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)} - \cos{\left(x \right)}}\right)$$
=
Introducimos una pequeña modificación de la función bajo el signo del límite
$$\lim_{x \to 0^+}\left(\frac{x \left(1 - x\right) \left(x + 1\right)^{2} \operatorname{acot}{\left(x \right)}}{\left(\cos{\left(x \right)} - 1\right) \cos{\left(x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \frac{x \left(1 - x\right) \left(x + 1\right)^{2} \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}}}{\frac{d}{d x} \left(\cos{\left(x \right)} - 1\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{- \frac{x^{4} \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} + \frac{x^{4}}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} - \frac{x^{3} \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} - \frac{4 x^{3} \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}} + \frac{x^{3}}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} + \frac{x^{2} \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} - \frac{3 x^{2} \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}} - \frac{x^{2}}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} + \frac{x \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} + \frac{2 x \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}} - \frac{x}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} + \frac{\operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}}}{\sin{\left(x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{- \frac{x^{4} \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} + \frac{x^{4}}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} - \frac{x^{3} \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} - \frac{4 x^{3} \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}} + \frac{x^{3}}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} + \frac{x^{2} \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} - \frac{3 x^{2} \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}} - \frac{x^{2}}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} + \frac{x \sin{\left(x \right)} \operatorname{acot}{\left(x \right)}}{\cos^{2}{\left(x \right)}} + \frac{2 x \operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}} - \frac{x}{x^{2} \cos{\left(x \right)} + \cos{\left(x \right)}} + \frac{\operatorname{acot}{\left(x \right)}}{\cos{\left(x \right)}}}{\sin{\left(x \right)}}\right)$$
=
$$-\infty$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 1 vez (veces)