English
If A is a simple ring and ι is a finite nonempty index type, then the matrix ring Matrix ι ι A is simple.
Русский
Если A простое кольцо и ι — конечный ненулевой индекс, то матричное кольцо Matrix ι ι A простое.
LaTeX
$$IsSimpleRing A ⇒ IsSimpleRing (Matrix ι ι A) for finite ι with Nonempty ι.$$
Lean4
instance matrix [IsSimpleRing A] : IsSimpleRing (Matrix ι ι A) where
simple :=
letI := Classical.decEq ι;
TwoSidedIdeal.orderIsoMatrix |>.symm.isSimpleOrder