Calculate a unit normal to (-5, 3)T.
(3, 5)/( √34). Or you might pick the other one (there are two): (-3, -5)/( √34).
Vectors in three dimensions, also, have unit normals. But a unit normal vector to a given vector is not unique. Think of the axle of a wagon wheel. All the spokes are orthogonal to the axle. Any line in the plane of the spokes is orthogonal to the axle; and there are an infinite number of them.
Find several normals to the vector represented by (1, 2, 2)T.