proposition: Theorem ps_mul_comm : ∀ ps₁ ps₂, (ps₁ * ps₂ = ps₂ * ps₁)%ps.
proof: Proof. intros ps₁ ps₂. constructor. apply ps_normal_mul_comm. Qed.
imports: Utf8 QArith NPeano Misc NbarM Field2 Fsummation Power_series Puiseux_series Ps_add Ps_add_compat