Tenemos la indeterminación de tipo
0/0,
tal que el límite para el numerador es
$$\lim_{x \to 0^+}\left(- x \cos{\left(x \right)} - \sqrt{x^{2} + 1} + e^{\sin{\left(x \right)}}\right) = 0$$
y el límite para el denominador es
$$\lim_{x \to 0^+} \log{\left(1 - x \right)}^{3} = 0$$
Vamos a probar las derivadas del numerador y denominador hasta eliminar la indeterminación.
$$\lim_{x \to 0^+}\left(\frac{\left(- x \cos{\left(x \right)} - \sqrt{x^{2} + 1}\right) + e^{\sin{\left(x \right)}}}{\log{\left(1 - x \right)}^{3}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(- x \cos{\left(x \right)} - \sqrt{x^{2} + 1} + e^{\sin{\left(x \right)}}\right)}{\frac{d}{d x} \log{\left(1 - x \right)}^{3}}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{\left(1 - x\right) \left(x \sin{\left(x \right)} - \frac{x}{\sqrt{x^{2} + 1}} + e^{\sin{\left(x \right)}} \cos{\left(x \right)} - \cos{\left(x \right)}\right)}{3 \log{\left(1 - x \right)}^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(- \frac{x \sin{\left(x \right)} - \frac{x}{\sqrt{x^{2} + 1}} + e^{\sin{\left(x \right)}} \cos{\left(x \right)} - \cos{\left(x \right)}}{3 \log{\left(1 - x \right)}^{2}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(x \sin{\left(x \right)} - \frac{x}{\sqrt{x^{2} + 1}} + e^{\sin{\left(x \right)}} \cos{\left(x \right)} - \cos{\left(x \right)}\right)}{\frac{d}{d x} \left(- 3 \log{\left(1 - x \right)}^{2}\right)}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\left(1 - x\right) \left(\frac{x^{2}}{\left(x^{2} + 1\right)^{\frac{3}{2}}} + x \cos{\left(x \right)} - e^{\sin{\left(x \right)}} \sin{\left(x \right)} + e^{\sin{\left(x \right)}} \cos^{2}{\left(x \right)} + 2 \sin{\left(x \right)} - \frac{1}{\sqrt{x^{2} + 1}}\right)}{6 \log{\left(1 - x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{x^{2}}{x^{2} \sqrt{x^{2} + 1} + \sqrt{x^{2} + 1}} + x \cos{\left(x \right)} - e^{\sin{\left(x \right)}} \sin{\left(x \right)} + e^{\sin{\left(x \right)}} \cos^{2}{\left(x \right)} + 2 \sin{\left(x \right)} - \frac{1}{\sqrt{x^{2} + 1}}}{6 \log{\left(1 - x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{\frac{d}{d x} \left(\frac{x^{2}}{x^{2} \sqrt{x^{2} + 1} + \sqrt{x^{2} + 1}} + x \cos{\left(x \right)} - e^{\sin{\left(x \right)}} \sin{\left(x \right)} + e^{\sin{\left(x \right)}} \cos^{2}{\left(x \right)} + 2 \sin{\left(x \right)} - \frac{1}{\sqrt{x^{2} + 1}}\right)}{\frac{d}{d x} 6 \log{\left(1 - x \right)}}\right)$$
=
$$\lim_{x \to 0^+}\left(\left(\frac{x}{6} - \frac{1}{6}\right) \left(\frac{x^{2} \left(- \frac{x^{3}}{\sqrt{x^{2} + 1}} - 2 x \sqrt{x^{2} + 1} - \frac{x}{\sqrt{x^{2} + 1}}\right)}{\left(x^{2} \sqrt{x^{2} + 1} + \sqrt{x^{2} + 1}\right)^{2}} - x \sin{\left(x \right)} + \frac{2 x}{x^{2} \sqrt{x^{2} + 1} + \sqrt{x^{2} + 1}} + \frac{x}{\left(x^{2} + 1\right)^{\frac{3}{2}}} - 3 e^{\sin{\left(x \right)}} \sin{\left(x \right)} \cos{\left(x \right)} + e^{\sin{\left(x \right)}} \cos^{3}{\left(x \right)} - e^{\sin{\left(x \right)}} \cos{\left(x \right)} + 3 \cos{\left(x \right)}\right)\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x^{5}}{6 x^{6} \sqrt{x^{2} + 1} + 18 x^{4} \sqrt{x^{2} + 1} + 18 x^{2} \sqrt{x^{2} + 1} + 6 \sqrt{x^{2} + 1}} + \frac{x^{3} \sqrt{x^{2} + 1}}{3 \left(x^{6} + 3 x^{4} + 3 x^{2} + 1\right)} + \frac{x^{3}}{6 x^{6} \sqrt{x^{2} + 1} + 18 x^{4} \sqrt{x^{2} + 1} + 18 x^{2} \sqrt{x^{2} + 1} + 6 \sqrt{x^{2} + 1}} + \frac{x \sin{\left(x \right)}}{6} - \frac{x}{2 \left(x^{2} \sqrt{x^{2} + 1} + \sqrt{x^{2} + 1}\right)} + \frac{e^{\sin{\left(x \right)}} \sin{\left(x \right)} \cos{\left(x \right)}}{2} - \frac{e^{\sin{\left(x \right)}} \cos^{3}{\left(x \right)}}{6} + \frac{e^{\sin{\left(x \right)}} \cos{\left(x \right)}}{6} - \frac{\cos{\left(x \right)}}{2}\right)$$
=
$$\lim_{x \to 0^+}\left(\frac{x^{5}}{6 x^{6} \sqrt{x^{2} + 1} + 18 x^{4} \sqrt{x^{2} + 1} + 18 x^{2} \sqrt{x^{2} + 1} + 6 \sqrt{x^{2} + 1}} + \frac{x^{3} \sqrt{x^{2} + 1}}{3 \left(x^{6} + 3 x^{4} + 3 x^{2} + 1\right)} + \frac{x^{3}}{6 x^{6} \sqrt{x^{2} + 1} + 18 x^{4} \sqrt{x^{2} + 1} + 18 x^{2} \sqrt{x^{2} + 1} + 6 \sqrt{x^{2} + 1}} + \frac{x \sin{\left(x \right)}}{6} - \frac{x}{2 \left(x^{2} \sqrt{x^{2} + 1} + \sqrt{x^{2} + 1}\right)} + \frac{e^{\sin{\left(x \right)}} \sin{\left(x \right)} \cos{\left(x \right)}}{2} - \frac{e^{\sin{\left(x \right)}} \cos^{3}{\left(x \right)}}{6} + \frac{e^{\sin{\left(x \right)}} \cos{\left(x \right)}}{6} - \frac{\cos{\left(x \right)}}{2}\right)$$
=
$$- \frac{1}{2}$$
Como puedes ver, hemos aplicado el método de l'Hopital (utilizando la derivada del numerador y denominador) 3 vez (veces)