Changes

= Border matrices with {{cmd|startbbordermatrixstartbordermatrix}} =

\startbbordermatrixstartbordermatrix\NC \NC {\bi col 1 } \NC cold {\bi col 2 } \NC {\bi col 3 }\NR\NC row 1 \NC a_{11} \NC a_{12} \NC a_{13} \NR\NC row 2 \NC a_{21} \NC a_{22} \NC a_{23} \NR\NC row 3 \NC a_{31} \NC a_{32} \NC a_{33} \NR\stopbbordermatrixstopbordermatrix

A second version, with Use {{cmd|startmatrixstartbordermatrix}} and using {{cmd|TT}} to define indexes. for a bracketed version:

\startmatrix[left={startbbordermatrix\left(},right={NC \right)}]\TT NC {\bi col 1} \TT NC {\bi col 2} \TT NC {\bi col 3}\NR\NC row 1 \NC a_{11} \NC a_{12} \NC a_{13} \NR\NC row 2 \NC a_{21} \NC a_{22} \NC a_{23} \NR\NC row 3 \NC a_{31} \NC a_{32} \NC a_{33} \NR\stopmatrixstopbbordermatrix