NCERT Example 23 - Vector Algebra
Question: Find a unit vector perpendicular to each of (a+b) and (a-b), where a = i-hat + j-hat + k-hat and b = i-hat + 2 j-hat + 3 k-hat.
Answer: ± (-i-hat + 2 j-hat - k-hat)/sqrt(6).
Full step-by-step NCERT solution with diagrams on Something by Zero.