Fabrice Couvreur schrieb am 13.05.2019 um 22:45:

Hi,
Not having too many ideas, I did this: is there not a more elegant way ?

\definemathmatrix [pmatrix] [matrix:parentheses] [simplecommand=MATRIX]

\starttext

\startformula
\startmathalignment
\NC P \times M = P \NC \iff \MATRIX{x,y} \times \MATRIX{0.22,0.78;0.53,0.47} = \MATRIX{x,y} \NR
\NC                \NC \iff
    \startmathcases
    \NC 0.22x + 0.53y = x \NR
    \NC 0.78x + 0.47y = y \NR
    \stopmathcases
\NR
\NC                \NC \iff 0.78x - 0.53y = 0 \NR
\NC                \NC \iff   78x -   53y = 0 \NR
\stopmathalignment
\stopformula

\stoptext

Wolfgang