Say that is the vector that results from taking the cross product of and .
You should recall that is perpendicular to both and .
Im hoping this is in right place?
Ok, am very stuck with this =(.
Find a vector perpendicular to both i + 2k - k and 3i -j + k.
Im sure its very simple..i know it is but i just can't do it =/...the answer is i - 4j - 7k.
I would greatly appreciate a poke in the right direction
Even if you didn't know about the cross product,
. . we can still answer the question.
Of course, it takes longer . . .
We are given two vectors: .Find a vector perpendicular to both and
We want a vector, , perpendicular to both and
Recall that two vectors are perpendicular if their dot product is zero.
Add  and : .
Substitute into : .
We have: .
On the right, replace with a parameter : .
This represents all vectors perpendicular to both and
Let and we have: .