English
If N is equipped with the discrete topology, then any multiplication map (hence in particular multiplication) is continuous; i.e., a discrete topological space makes every algebraic operation continuous.
Русский
Если у пространства N задан дискретный топологический структура, то любая операция умножения неприменима, т.е. непрерывна.
LaTeX
$$$[TopologicalSpace\\,N] \\land [Mul\\,N] \\land [DiscreteTopology\\,N] \\Rightarrow \\text{ContinuousMul}\\,N$$$
Lean4
@[to_additive]
instance (priority := 100) continuousMul_of_discreteTopology [TopologicalSpace N] [Mul N] [DiscreteTopology N] :
ContinuousMul N :=
⟨continuous_of_discreteTopology⟩