if given two vectors that are parallel how can you find an orthogonal vector? the cross product is the zero vector.
If two vectors are parallel then any vector that is orthogonal to one is orthogonal to the other. And, in three dimensions, there exist an infinite number of vectors orthogonal to a given vector. If the given vector is <a, b, c> then <x, y, z> is orthogonal to it as long as ax+ by+ cz= 0. Choose any value for any two of x, y, and z and solve for the other.
so just take the cross product of one of the given vectors and a 'cooked up' vector thats not a scalar multiple of the two given
question says to describe all unit vectors orthogonal that'd be $\displaystyle \pm \frac{\vec{n}}{||\vec{n}||}$ correct?