1. The problem statement, all variables and given/known data I'm trying to express the conditions for a zigzag carbon nanotube in a mathematical vector. 2. Relevant equations B = na1 + ma2 3. The attempt at a solution I want to say "either a=0 or b=0", but must I also say that it can't be a=b=0 or is that already excluded in the statement? I'm not sure of the mathematical logic at work. Thanks in advance P.S B, a1 and a2 are vectors, but I couldn't find the bold button.