In
linear algebra, the
main diagonal (sometimes
principal diagonal,
primary diagonal,
leading diagonal, or
major diagonal) of a matrix
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=1980)
is the collection of entries
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=3435)
where . The following three matrices have their main diagonals indicated by red 1's:
The
antidiagonal (sometimes
counterdiagonal,
secondary diagonal,
trailing diagonal or
minor diagonal) of a dimension
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=668)
square matrix,
![](http://info.babylon.com/onlinebox.cgi?rt=GetFile&uri=!!ARV6FUJ2JP&type=0&index=507)
, is the collection of entries such that . That is, it runs from the top right corner to the bottom left corner:
See also