1. Position vector r DOT n(hat) = a, where n(hat) is a unit vector and a is a scalar. 2. Position vector r DOT n(hat) = a times (magnitude of) r. I know the first question describes a plane of n = a, if n is a Cartesian unit vector. However I don't know if I should worry about other unit vectors. The second question I would think the plane just changes by mag of r, but that seems too simple. Thanks for any help.