Problem 3: Problem Solving Cross Product
Problem3.1 Find a unit vector perpendicular to A=i+j-k and B=-2i-j+3k: Answer given for k-component is ((1)(-1)-(1)(2)) k = -3k. Should not the 2 be negative: ((1)(-1)-(1)(-2)) k = +1k? because B's i-component is -2? e.g. (AxBy - AyBx)k

Question

Problem 3: Problem Solving Cross Product
Problem3.1 Find a unit vector perpendicular to A=i+j-k and B=-2i-j+3k: Answer given for k-component is ((1)(-1)-(1)(2)) k = -3k.  Should not the 2 be negative: ((1)(-1)-(1)(-2)) k = +1k?  because B's i-component is -2? e.g. (AxBy - AyBx)k

anonymous · Answer

I haven't got the problem in front of me, but yes, I do remember thinking the same thing you did on that question.  IIRC, if you look at one of their intermediary steps, you can see where the error snuck in, and all the work from then onwards is correct.