Geodesic
Compositions of linear-fractional transformations
Matematičeskie zametki, Tome 61 (1997) no. 3, pp. 332-338 
V. I. Buslaev; S. F. Buslaeva. Compositions of linear-fractional transformations. Matematičeskie zametki, Tome 61 (1997) no. 3, pp. 332-338. http://geodesic.mathdoc.fr/item/MZM_1997_61_3_a1/
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     author = {V. I. Buslaev and S. F. Buslaeva},
     title = {Compositions of linear-fractional transformations},
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     pages = {332--338},
     year = {1997},
     volume = {61},
     number = {3},
     language = {ru},
     url = {http://geodesic.mathdoc.fr/item/MZM_1997_61_3_a1/}
}
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Voir la notice de l'article provenant de la source Math-Net.Ru

We study the asymptotic behavior of the compositions $(\mathbf S_n\circ\dots\circ\mathbf S_1)(z)$ and $(\mathbf S_1\circ\dots\circ\mathbf S_n)(z)$ of linear-fractional transformations $\mathbf S_n(z)$ ($n=1,2,\dots$) whose fixed points have limits. In particular, if $\mathbf S_n(z)=\alpha_n(\beta_n+z)^{-1}$, then the sequence of compositions $(\mathbf S_1\circ\dots\circ\mathbf S_n)(z)$ at the point $z=0$ coincides with the sequence of convergents of the formal continued fraction $$ \frac{\alpha_1}{\beta_1+\dfrac{\alpha_2}{\beta_2+\dotsb}}. $$ The result obtained can be applied in the study of convergence of formal continued fractions.

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