∀ {R : Type u_1} [inst : Semiring R] {M₁ : Type u_2} [inst_1 : TopologicalSpace M₁] [inst_2 : AddCommMonoid M₁]
  [inst_3 : Module R M₁] {M₂ : Type u_3} [inst_4 : TopologicalSpace M₂] [inst_5 : AddCommMonoid M₂]
  [inst_6 : Module R M₂] {M₃ : Type u_4} [inst_7 : TopologicalSpace M₃] [inst_8 : AddCommMonoid M₃]
  [inst_9 : Module R M₃] (f : M₁ →L[R] M₂) (g : M₁ →L[R] M₃), (↑(f.prod g)).ker = (↑f).ker ⊓ (↑g).ker