Does the output of this system have a closed form expression?

1. What does it mean when an expression is closed?
2. What is closed-form approximation?
3. What is no closed-form solution?

What does it mean when an expression is closed?

A closed expression (or closed formula) refers to a formula that has no free variables [1]. This is also called sentence. In a logic system, you have a set of axioms, which are sentences, and rules which state how to derive a sentence from this [2].

What is closed-form approximation?

Abstract. A closed-form analytical approximation is derived for the response transition probability density function (PDF) of a certain class of stochastic differential equations with constant drift and nonlinear diffusion coefficients.

What is no closed-form solution?

A closed form solution provides an exact answer and one that is not closed form is an approximation, but you can get a non closed form solution as close as to a closed form solution as you want. Sounds counter intuitive, but if you need it more accurate, then just grind out a little bit more computations.