English
BlockDiagonal distributes over addition: blockDiagonal(M + N) = blockDiagonal(M) + blockDiagonal(N).
Русский
Блочная диагональ распределяется по сложению: blockDiagonal(M + N) = blockDiagonal(M) + blockDiagonal(N).
LaTeX
$$$\operatorname{blockDiagonal}(M+N) = \operatorname{blockDiagonal}(M) + \operatorname{blockDiagonal}(N).$$$
Lean4
@[simp]
theorem blockDiagonal_add [AddZeroClass α] (M N : o → Matrix m n α) :
blockDiagonal (M + N) = blockDiagonal M + blockDiagonal N :=
by
ext
simp only [blockDiagonal_apply, Pi.add_apply, add_apply]
split_ifs <;> simp