We have indeterminateness of type
oo/oo, i.e. limit for the numerator is
lim x → ∞ 1 tan ( 1 x + 1 ) = ∞ \lim_{x \to \infty} \frac{1}{\tan{\left(\frac{1}{x + 1} \right)}} = \infty x → ∞ lim tan ( x + 1 1 ) 1 = ∞ and limit for the denominator is
lim x → ∞ 1 tan ( 1 x ) = ∞ \lim_{x \to \infty} \frac{1}{\tan{\left(\frac{1}{x} \right)}} = \infty x → ∞ lim tan ( x 1 ) 1 = ∞ Let's take derivatives of the numerator and denominator until we eliminate indeterninateness.
lim x → ∞ ( tan ( 1 x ) tan ( 1 x + 1 ) ) \lim_{x \to \infty}\left(\frac{\tan{\left(\frac{1}{x} \right)}}{\tan{\left(\frac{1}{x + 1} \right)}}\right) x → ∞ lim ( tan ( x + 1 1 ) tan ( x 1 ) ) =
lim x → ∞ ( d d x 1 tan ( 1 x + 1 ) d d x 1 tan ( 1 x ) ) \lim_{x \to \infty}\left(\frac{\frac{d}{d x} \frac{1}{\tan{\left(\frac{1}{x + 1} \right)}}}{\frac{d}{d x} \frac{1}{\tan{\left(\frac{1}{x} \right)}}}\right) x → ∞ lim d x d t a n ( x 1 ) 1 d x d t a n ( x + 1 1 ) 1 =
lim x → ∞ ( x 2 ( tan 2 ( 1 x + 1 ) + 1 ) tan 2 ( 1 x ) ( x + 1 ) 2 ( tan 2 ( 1 x ) + 1 ) tan 2 ( 1 x + 1 ) ) \lim_{x \to \infty}\left(\frac{x^{2} \left(\tan^{2}{\left(\frac{1}{x + 1} \right)} + 1\right) \tan^{2}{\left(\frac{1}{x} \right)}}{\left(x + 1\right)^{2} \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right) \tan^{2}{\left(\frac{1}{x + 1} \right)}}\right) x → ∞ lim ( ( x + 1 ) 2 ( tan 2 ( x 1 ) + 1 ) tan 2 ( x + 1 1 ) x 2 ( tan 2 ( x + 1 1 ) + 1 ) tan 2 ( x 1 ) ) =
lim x → ∞ ( 1 ( 1 tan 2 ( 1 x ) + 2 x tan 2 ( 1 x ) + 1 x 2 tan 2 ( 1 x ) ) tan 2 ( 1 x + 1 ) ) \lim_{x \to \infty}\left(\frac{1}{\left(\frac{1}{\tan^{2}{\left(\frac{1}{x} \right)}} + \frac{2}{x \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{1}{x^{2} \tan^{2}{\left(\frac{1}{x} \right)}}\right) \tan^{2}{\left(\frac{1}{x + 1} \right)}}\right) x → ∞ lim ( t a n 2 ( x 1 ) 1 + x t a n 2 ( x 1 ) 2 + x 2 t a n 2 ( x 1 ) 1 ) tan 2 ( x + 1 1 ) 1 =
lim x → ∞ ( d d x 1 tan 2 ( 1 x + 1 ) d d x ( 1 tan 2 ( 1 x ) + 2 x tan 2 ( 1 x ) + 1 x 2 tan 2 ( 1 x ) ) ) \lim_{x \to \infty}\left(\frac{\frac{d}{d x} \frac{1}{\tan^{2}{\left(\frac{1}{x + 1} \right)}}}{\frac{d}{d x} \left(\frac{1}{\tan^{2}{\left(\frac{1}{x} \right)}} + \frac{2}{x \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{1}{x^{2} \tan^{2}{\left(\frac{1}{x} \right)}}\right)}\right) x → ∞ lim d x d ( t a n 2 ( x 1 ) 1 + x t a n 2 ( x 1 ) 2 + x 2 t a n 2 ( x 1 ) 1 ) d x d t a n 2 ( x + 1 1 ) 1 =
lim x → ∞ ( 2 ( tan 2 ( 1 x + 1 ) + 1 ) ( x + 1 ) 2 ( 2 ( tan 2 ( 1 x ) + 1 ) x 2 tan 3 ( 1 x ) − 2 x 2 tan 2 ( 1 x ) + 4 ( tan 2 ( 1 x ) + 1 ) x 3 tan 3 ( 1 x ) − 2 x 3 tan 2 ( 1 x ) + 2 ( tan 2 ( 1 x ) + 1 ) x 4 tan 3 ( 1 x ) ) tan 3 ( 1 x + 1 ) ) \lim_{x \to \infty}\left(\frac{2 \left(\tan^{2}{\left(\frac{1}{x + 1} \right)} + 1\right)}{\left(x + 1\right)^{2} \left(\frac{2 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{2} \tan^{3}{\left(\frac{1}{x} \right)}} - \frac{2}{x^{2} \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{4 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{3} \tan^{3}{\left(\frac{1}{x} \right)}} - \frac{2}{x^{3} \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{2 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{4} \tan^{3}{\left(\frac{1}{x} \right)}}\right) \tan^{3}{\left(\frac{1}{x + 1} \right)}}\right) x → ∞ lim ( x + 1 ) 2 ( x 2 t a n 3 ( x 1 ) 2 ( t a n 2 ( x 1 ) + 1 ) − x 2 t a n 2 ( x 1 ) 2 + x 3 t a n 3 ( x 1 ) 4 ( t a n 2 ( x 1 ) + 1 ) − x 3 t a n 2 ( x 1 ) 2 + x 4 t a n 3 ( x 1 ) 2 ( t a n 2 ( x 1 ) + 1 ) ) tan 3 ( x + 1 1 ) 2 ( tan 2 ( x + 1 1 ) + 1 ) =
lim x → ∞ ( 2 ( x + 1 ) 2 ( 2 ( tan 2 ( 1 x ) + 1 ) x 2 tan 3 ( 1 x ) − 2 x 2 tan 2 ( 1 x ) + 4 ( tan 2 ( 1 x ) + 1 ) x 3 tan 3 ( 1 x ) − 2 x 3 tan 2 ( 1 x ) + 2 ( tan 2 ( 1 x ) + 1 ) x 4 tan 3 ( 1 x ) ) tan 3 ( 1 x + 1 ) ) \lim_{x \to \infty}\left(\frac{2}{\left(x + 1\right)^{2} \left(\frac{2 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{2} \tan^{3}{\left(\frac{1}{x} \right)}} - \frac{2}{x^{2} \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{4 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{3} \tan^{3}{\left(\frac{1}{x} \right)}} - \frac{2}{x^{3} \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{2 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{4} \tan^{3}{\left(\frac{1}{x} \right)}}\right) \tan^{3}{\left(\frac{1}{x + 1} \right)}}\right) x → ∞ lim ( x + 1 ) 2 ( x 2 t a n 3 ( x 1 ) 2 ( t a n 2 ( x 1 ) + 1 ) − x 2 t a n 2 ( x 1 ) 2 + x 3 t a n 3 ( x 1 ) 4 ( t a n 2 ( x 1 ) + 1 ) − x 3 t a n 2 ( x 1 ) 2 + x 4 t a n 3 ( x 1 ) 2 ( t a n 2 ( x 1 ) + 1 ) ) tan 3 ( x + 1 1 ) 2 =
lim x → ∞ ( 2 ( x + 1 ) 2 ( 2 ( tan 2 ( 1 x ) + 1 ) x 2 tan 3 ( 1 x ) − 2 x 2 tan 2 ( 1 x ) + 4 ( tan 2 ( 1 x ) + 1 ) x 3 tan 3 ( 1 x ) − 2 x 3 tan 2 ( 1 x ) + 2 ( tan 2 ( 1 x ) + 1 ) x 4 tan 3 ( 1 x ) ) tan 3 ( 1 x + 1 ) ) \lim_{x \to \infty}\left(\frac{2}{\left(x + 1\right)^{2} \left(\frac{2 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{2} \tan^{3}{\left(\frac{1}{x} \right)}} - \frac{2}{x^{2} \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{4 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{3} \tan^{3}{\left(\frac{1}{x} \right)}} - \frac{2}{x^{3} \tan^{2}{\left(\frac{1}{x} \right)}} + \frac{2 \left(\tan^{2}{\left(\frac{1}{x} \right)} + 1\right)}{x^{4} \tan^{3}{\left(\frac{1}{x} \right)}}\right) \tan^{3}{\left(\frac{1}{x + 1} \right)}}\right) x → ∞ lim ( x + 1 ) 2 ( x 2 t a n 3 ( x 1 ) 2 ( t a n 2 ( x 1 ) + 1 ) − x 2 t a n 2 ( x 1 ) 2 + x 3 t a n 3 ( x 1 ) 4 ( t a n 2 ( x 1 ) + 1 ) − x 3 t a n 2 ( x 1 ) 2 + x 4 t a n 3 ( x 1 ) 2 ( t a n 2 ( x 1 ) + 1 ) ) tan 3 ( x + 1 1 ) 2 =
1 1 1 It can be seen that we have applied Lopital's rule (we have taken derivatives with respect to the numerator and denominator) 2 time(s)