If I have well understood, in the trinomial model we have a kind of risk neutral pricing formula that depends on a parameter. This means thaht as in the binomial model, we could use directly this formula to obtain the price of an option (European type) if there was not this dependency on a parameter. So the problem is to find the value of the parameter that gives a "fair price" ? However, in all I have mentioned, we do not talk about the hedging, so what link can be made with the hedging if there is one ?
In the binomial, it is clear since we can find by backward induction the perfect hedging and thus the price.