This node for the Unity Shader Graph converts 2D coordinates from Polar Coordinate form into standard UV Cartesian Coordinates.  It is the reverse of the Unity-provided Polar Coordinate node

Requires Shader Graph package version 7.1.5 or later.

Cartesian coordinates, also known as rectangular coordinates, are used to represent a two dimensional point by an x and y offset. UV coordinates used for texture sampling are in this form. In Polar form, this point is instead represented as a distance from the center, and angle of rotation.

Documentation

This is based on a tutorial on gamedevbill.com about creating custom nodes. This tutorial includes an in depth description of what's going on in the shader, source included. It is part of an ongoing shader tutorial series