от Гост » 30 Ное 2012, 19:48
[tex]\lim_{x \to +\infty} \, (x+1) \operatorname{acot} x[/tex]
[tex]\operatorname{acot}x = t \Rightarrow x = \cot t = \frac{\cos t}{\sin t}; \quad x \to +\infty \Rightarrow t \to 0[/tex]
[tex]\lim_{t \to 0} \, t(\frac{\cos t}{\sin t} + 1) = \lim_{t \to 0} \frac{t(\cos t + \sin t)}{\sin t} = \lim_{t \to 0} \frac{t \cos t + t \sin t}{\sin t} = \lim_{t \to 0} \frac{\cos t - t \sin t + \sin t + t \cos t}{\cos t} = 1[/tex]