English
A non-unital seminormed ring has a continuous multiplication operation with respect to its norm.
Русский
У нетривиального неполного нормированного кольца существует непрерывное умножение относительно норм.
LaTeX
$$$ \\text{ContinuousMul}(\\alpha) \\text{ given by } \\|xy\\| \\le \\|x\\| \\|y\\|.$$$
Lean4
/-- Normed commutative ring structure on the product of finitely many non-unital normed
commutative rings, using the sup norm. -/
instance nonUnitalNormedCommRing {R : ι → Type*} [Fintype ι] [∀ i, NonUnitalNormedCommRing (R i)] :
NonUnitalNormedCommRing (∀ i, R i) :=
{ Pi.nonUnitalSeminormedCommRing, Pi.normedAddCommGroup with }