Hi, it's been a while since I've attempted anything to do with vectors and I'm a little rusty at the moment.
The question is:
Fine a vector length anti-parallel to .
I thought that maybe the vector product would be the way forward but no idea where to start.
Any help would be greatly appreciated.
Thanks
Craig
Any vector parallel to (-1, 2, -1) must be of the form a(-1, 2, -1)= (-a, 2a, -a). Any vector anti-parallel to (-1, 2, -1) (in the opposite direction) must be of that form with a negative- or we can write it -a(-1, 2, -1)= (a, -2a, a) with the requirement that a be positive.
Now, the length of (a, -2a, a) is . In order that the vector have length , we must have or a= 2. (a, -2a, a)= (2, -4, 2).