Unit Vector

robphy

possibly useful:
http://www.frontiernet.net/~imaging/...alculator.html

HallsofIvy

Yes, if [tex]\frac{\vec u}{|\vec u|} = \frac{\vec v}{|\vec v|}[/tex]
then two vectors are "in the same direction".

Notice that that also implies [tex]\vec{u}= \frac{|\vec{u}|}{|\vec{v}|} \vec{v}[/itex]. That is, two vectors are in the same direction (parallel) if and only if one is a positive multiple of the other. That's often easier to show since it doesn't involve messing with square roots!

(If one is a negative multiple of the other, they point in opposite directions (anti-parallel).)