# Poisson’s Integral Formulas?

It is known the Poisson's integral formula : Let $$f(z)$$ be analytic inside and on the circle $$\mathcal{C} : \vert z \vert = R$$, and let $$z =re^{i \theta}$$ be any point inside $$\mathcal{C}$$ so :

$$f(re^{i \theta}) = \dfrac{1}{2\pi} \int_{0}^{2\pi} \dfrac{R^2-r^2}{R^2 - 2Rr\cos(\theta - \phi) + r^2}f(Re^{i \phi})\,d\phi$$

In one task they ask me to find the Poisson's integral formula (if possible) in a square.

How could I do it?. I was thinking of doing the same for the case of the circle but I don't know if that's what the problem refers to. Any help or hint it would help me a lot.