# Vectors in three dimensions

• May 4th 2009, 04:14 PM
ep78
Vectors in three dimensions
find the value of k if (2,k,-3) and (4,2,6) are perpendicular

Thank you
• May 4th 2009, 04:48 PM
VonNemo19
Doesn't the two coordinates you gave correspond to 2 points in space?
If so, how can 2 points be perpidicular?
• May 4th 2009, 05:26 PM
skeeter
Quote:

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 $k$