diff options
Diffstat (limited to 'library/cardinal.tex')
| -rw-r--r-- | library/cardinal.tex | 10 |
1 files changed, 9 insertions, 1 deletions
diff --git a/library/cardinal.tex b/library/cardinal.tex index d0dec59..5682619 100644 --- a/library/cardinal.tex +++ b/library/cardinal.tex @@ -1,8 +1,9 @@ -\section{Cardinality} +\section{Cardinality}\label{form_sec_cardinality} \import{set.tex} \import{ordinal.tex} \import{function.tex} +\import{numbers.tex} \begin{definition}\label{finite} $X$ is finite iff there exists a natural number $k$ such that @@ -12,3 +13,10 @@ \begin{abbreviation}\label{infinite} $X$ is infinite iff $X$ is not finite. \end{abbreviation} + +\begin{definition}\label{cardinality} + $X$ has cardinality $k$ iff $k$ is a natural number and + there exists a bijection from $k$ to $X$. +\end{definition} + + |