Use f_equal.
Use f_equal.
Let w be given.
We will prove g w = h w.
Apply SNoR_E x Hx w Hw to the current goal.
Assume Hw1 Hw2 Hw3.
Apply Hgh to the current goal.
We will
prove w ∈ SNoS_ (SNoLev x).
An exact proof term for the current goal is SNoS_I2 w x Hw1 Hx Hw2.