∀ {R : Type u} {A : Type v} [inst : CommSemiring R] [inst_1 : AddCommMonoid A] [inst_2 : Module R A]
  [inst_3 : Coalgebra R A] (a : A),
  (TensorProduct.assoc R A A A).symm ((LinearMap.lTensor A CoalgebraStruct.comul) (CoalgebraStruct.comul a)) =
    (LinearMap.rTensor A CoalgebraStruct.comul) (CoalgebraStruct.comul a)