The cross product of the vectors will be orthogonal to both: axb [tex]=<1,3,1>x<1,12,1> = i j k 1 3 1 1 12 1 =<3-12, -1+1, 12-3> =<-9,0,9> Since it is required to have positive first coordinate, we reverse the sign of the components, namely reverse the direction of the vector, which is still orthogonal to both a and b: Required vector is <9,0,-9> which is orthogonal to both a and b.
