Question

PLEASE HELP! I'm having trouble with these two problems. Click attached

Answer 1

use
\[ A \cdot B = |A| |B| cos(\theta) \]

along with the alternate definition of dot product
(ax, ay,az) dot (bx,by,bz)= ax*bx + ay*by + az*bz

remember, when perpendicular theta is 90º

Answer 2

For the first one, we want <x,2> perpendicular to <3,12>
x = -8

Answer 3

Thanks guys! You both deserve medals but I can only give one :/

Answer 4

I gave him one.