Note to exercise 1-03 a)

I did a mistake when I solved exercise 1-03 a) on the blackboard. I told that you could use two kind of arguments, both using that the dot product of any two vectors are non-zero, or showing that one of the vectors is a linear sum of the other two.

However, my method of using dot product is incorrect! What is true for dot products is that when the dot product is zero, then the vectors are linear independent. But the opposite is not true. That is: it may be that two vectors are linear independent, even though the dot product is not zero. Thus, by showing that the dot product is not zero, I have not proven that the vectors are not linear independent!

Sorry about this confusion!

Espen