# Thread: what does this mean!!! vector stuff!!!

1. ## what does this mean!!! vector stuff!!!

find all vectors v = [x, y, z] orthogonal [perpendicular] to both u1 = [3 -1 2] and u2 = [2 0 1]

please explain what does it mean....like what should i do with this...
?????

2. Originally Posted by bullmaster
find all vectors v = [x, y, z] orthogonal [perpendicular] to both u1 = [3 -1 2] and u2 = [2 0 1]

please explain what does it mean....like what should i do with this...
?????
The vector you're looking for is going to be a nonzero multiple of the cross product u1 x u2.

Can you take it from here?

3. i dont think so..i am not getting it still....can u explain further please!!!!

Originally Posted by Chris L T521
The vector you're looking for is going to be a nonzero multiple of the cross product u1 x u2.

Can you take it from here?

4. Originally Posted by bullmaster
i dont think so..i am not getting it still....can u explain further please!!!!
Have you been taught the cross product (also called the vector product)?

5. yea i know vectors...but the way i did was in a different way...i dont understand what the question is asking me to do...if anyone could solve it for me...i would really appreciate....

thanks

Originally Posted by mr fantastic
Have you been taught the cross product (also called the vector product)?

6. Originally Posted by bullmaster
yea i know vectors...but the way i did was in a different way...i dont understand what the question is asking me to do...if anyone could solve it for me...i would really appreciate....

thanks
Have you been taught the cross product (also called the vector product)? Yes or no? And if you have done it in a different way, please show your work.

7. The problem is asking you to find a vector that is perpendicular to both [3 -1 2] and [2 0 1]. If you know how to find a cross product (and mr. fantastic has asked twice now if you do), that is the simplest thing to do. The cross product of two vectors is perpendicular to both.

If you do not, do you know that the two perpendicular vectors must have dotproduct equal to 0?

Write your vector as [a b c] and set the dot product of that with both [3 -1 2] and [2 0 1] equal to 0. That gives two equations for a, b, and c. That is not completely determined because there exist an infinite number of vectors perpendicular to two given vectors.