Definition:Convergent of Continued Fraction

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Not to be confused with Definition:Convergent Continued Fraction.

Definition

Let $F$ be a field, such as the field of real numbers.

Let $n \in \N \cup \{\infty\}$ be an extended natural number.

Let $C = \left[{a_0, a_1, a_2, \ldots}\right]$ be a continued fraction in $F$ of length $n$.

Let $k \leq n$ be a natural number.


Definition 1

The $k$th convergent $C_k$ of $C$ is the value of the finite continued fraction:

$C_k = \left[{a_0, a_1, \ldots, a_k}\right]$


Definition 2

The $k$th convergent $C_k$ of $C$ is the quotient of the $k$th numerator $p_k$ by the $k$th denominator $q_k$:

$C_k = \dfrac{p_k}{q_k}$


Even and odd convergents

Even Convergent

The even convergents of $\left[{a_0, a_1, a_2, \ldots}\right]$ are the convergents $C_0, C_2, C_4, \ldots$, that is, those with an even subscript.


Odd Convergent

The odd convergents of $\left[{a_0, a_1, a_2, \ldots}\right]$ are the convergents $C_1, C_3, C_5, \ldots$, that is, those with an odd subscript.


Also see