The problem statement, all variables and given/known data http://s2.ipicture.ru/uploads/20111115/ltM3iwGZ.jpg The attempt at a solution Please correct me if i'm wrong in my assumptions: R^4 means that i need to find a vector that exists in 4 dimensions, meaning 4 rows. I am trying desperately to visualise this problem, with 4 axis since it involves 4 dimensions, but i can't. How would 4 dimensions appear? I learned about 3 dimensions, using the right-handed system and the three axis; x, y, z, each axis perpendicular to each other. My basic understanding of this problem is that i have to solve this vector equation: axbxc, where a is the first column vector, b, is the second, and so on. However, in my undergraduate syllabus, it says it's called dyadics and it's beyond the scope of my programme. So, i'm thinking (axb)xc but this is not the same thing! unless i'm mistaken? Also, if the vector i need to find, is perpendicular to any two from the given vectors, it should naturally be perpendicular to the 3rd given vector, right?