English
In a topological monoid, if a path joins a to b and a path joins c to d, then their product path joins a c to b d.
Русский
В топологической группе/полугруппе с непрерывной операцией плавно складываются пути: если есть путь a→b и путь c→d, то есть путь a·c→b·d.
LaTeX
$$$Joined a b \to Joined c d \Rightarrow Joined (a*c) (b*d)$$$
Lean4
@[to_additive]
theorem mul {M : Type*} [Mul M] [TopologicalSpace M] [ContinuousMul M] {a b c d : M} (hs : Joined a b)
(ht : Joined c d) : Joined (a * c) (b * d) :=
⟨hs.somePath.mul ht.somePath⟩