Could someone please help me with a 3D vectors question? Posting below...

Question

anonymous · Answer

Lines L1 and L2 have equations $$r=<1 , 4 , -1> +\lambda <-1 , 2, 3> $$ and $$r = <0,-2,2> + \mu <-1, 1 ,-2>$$ Find the acute angle between L1 and L2 (without your calculator)

agent0smith · Answer

Been a long while, but can't you use the dot product?

anonymous · Answer

Do you use the position vectors or the direction vectors when you do the dot product? I'm kind of confused

anonymous · Answer

I used the direction vectors to do the dot product and I got cos(theta) = -3/8 and you can't really solve for theta without a calc so I'm obviously doing something wrong... :S

agent0smith · Answer

I think you have to use both position and direction. If i get a chance later I'll try to solve it... making food atm.