Ya never mind i just tested it.
float radsAsUnits = (atan2(input.TexureCoordinateA.x - 0.5f, input.TexureCoordinateA.y - 0.5f) / 3.14159265f) * 0.5f + 0.5f;
col.g = radsAsUnits;
col.a = 1.0f;
trying to do something really complicated just messing something else up.