English
A subalgebra of a normed commutative ring is itself a normed commutative ring by restricting the norm.
Русский
Подалгебра нормированного коммутативного кольца образует нормированное кольцо по ограничению нормы.
LaTeX
$$$\text{If } s \text{ is a Subalgebra of a NormedCommRing } E, \; s \text{ is a NormedCommRing with restricted norm.}$$$
Lean4
/-- A subalgebra of a normed commutative ring is also a normed commutative ring, with the
restriction of the norm. -/
instance normedCommRing {𝕜 : Type*} [CommRing 𝕜] {E : Type*} [NormedCommRing E] [Algebra 𝕜 E] (s : Subalgebra 𝕜 E) :
NormedCommRing s :=
{ s.seminormedCommRing, s.normedRing with }