# Unit Vector Question

• Mar 27th 2008, 01:56 PM
haku
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.
• Mar 27th 2008, 01:59 PM
bobak
are you familiar with cross products ? if so your answer is given by $\displaystyle \frac{u \times v}{|u \times v|}$
• Mar 27th 2008, 02:01 PM
haku
Yeh I can do cross products, thanks for the very quick responce and help!
• Mar 27th 2008, 02:11 PM
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. Can you help?
• Mar 27th 2008, 02:24 PM
Plato
Quote:

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.

You want to find values such that $\displaystyle \frac {1}{-3} = \frac {a}{1} = \frac {2b}{4}$.