# Thread: Unit Vector Question

1. ## Unit Vector Question

The question I am having problems with is:

Find a unit vector perpendicular to u = i+3k

and v = 2j-k.

Can anyone help me solve this?

I know that u.v = 0 if they are perpendicular, thanks.

2. are you familiar with cross products ? if so your answer is given by $\displaystyle \frac{u \times v}{|u \times v|}$

3. Yeh I can do cross products, thanks for the very quick responce and help!

4. I also have a problem solving this question:

Find the values of a and b such that u = (1,a,2b) and v = (-3,1,4) are parallel. I tried equating the terms but I'm not getting anywhere. a+8b-3=0. Can you help?

5. Originally Posted by haku
I also have a problem solving this question:
Find the values of a and b such that u = (1,a,2b) and v = (-3,1,4) are parallel. I tried equating the terms but I'm not getting anywhere. a+8b-3=0.
Please always start a new thread, do not add to an existing one.
You want to find values such that $\displaystyle \frac {1}{-3} = \frac {a}{1} = \frac {2b}{4}$.