# Thread: Vectors in three dimensions

1. ## Vectors in three dimensions

find the value of k if (2,k,-3) and (4,2,6) are perpendicular

Thank you

2. Doesn't the two coordinates you gave correspond to 2 points in space?
If so, how can 2 points be perpidicular?

3. Originally Posted by ep78
find the value of k if (2,k,-3) and (4,2,6) are perpendicular
two vectors are perpendicular if their dot product = 0

$\langle 2,k,-3 \rangle \bullet \langle 4,2,6 \rangle = 8 + 2k - 18 = 0$

solve for $k$