===== Unit matrix =====
==== Set ====
| @#55CCEE: context     | @#55CCEE: $n\in \mathbb N$ | 
| @#55CCEE: context     | @#55CCEE: $R$ ... ring | 

| @#FFBB00: definiendum | @#FFBB00: $ (I_n)_{ij} := \begin{cases} e & \mathrm{if}\ i=j\\\\ 0 & \mathrm{else} \end{cases}$ |

| @#55EE55: postulate   | @#55EE55: $ I_n \in \mathrm{SquareMatrix}(n,R) $ |

==== Discussion ====
=== Reference ===
Wikipedia: [[http://en.wikipedia.org/wiki/Unit_matrix|Unit matrix]]
==== Parents ====
=== Element of ===
[[Matrix ring]]