1. The problem statement, all variables and given/known data Let x and y be to vectors Verify whether |xy|<=|x|+|y| for all x,y 3. The attempt at a solution My first problem with this question is that it does not tell us whether the operation xy is the same as x.y (dot product) or a cross product.
Your are right. That is a problem. I am also surprised that is not [itex]|x|^2+ |y|^2[/itex] on the right. I suspect that they mean dot product. I suggest you look at [itex]|(x-y)\cdot(x-y)|[/itex].