I have a procedural texture with a circle made by formula X ** 2 + Y ** 2 < R ** 2. It looks like a circle on a plane. But if I try to use this formula in the World environment - the circle is distorted.

How to convert XY coordinates in the formula to the equirectangular coordinates to have the clear circle in the environment?

It’s not about especially for the circle, I need to have the formula to translate any procedurally generated plane texture to equirectangular.