“…Then there exist constants δ 0 > 0 and σ s > 0 depending on the background solution such that, for any −1 < σ ∞ ≤ 0 < σ 0 < σ s , if the wedge edge is not perturbed, that is, where K > 0 depends on the background solution, but is independent of δ 0 > 0. 4) is over-determined, which is exactly the instability mechanism for strong transonic solutions shown in [25]. In Theorem 5.2, since σ 0 > 0, estimate (5.6) yields that Du − Du 0 ≡ 0 on edge y 1 = 0, y 2 = 0, y ′ ∈ R n−2 , which indicates that, as the wedge edge is not perturbed such that (3.10) holds, conditions (5.4) hold automatically, and solution u(y) to problem (5.1)-(5.3) is indeed a solution to problem (5.1)-(5.4).…”