Question

2. If A = 21 + 3j - 2k B = 31 + +2j when both A & B
are perpendicular to
one another compute
​

Answer 1

When two vectors are perpendicular to each other then their dot product is always equal to 0. As per the vectors rules for dot product:

1. i.i=1

2. j.j=1

3. k.k=1

4. i.j=0

5. j.k=0

6. i.k=0

So if you remember these rules this question is quite easy to solve.What you have to do is multiply the two given vectors according to the dot products rules.

So we have, A.B=0

(2i+2j+3k).(3i+6k+nk)=0

2i.3i + 2j.0j + 3k.(6+n)k =0

6+3(6+n)=0

6+n=-2

n=-8

Therefore the value of n is -8 for the two vectors A and B to be perpendicular.

Hope it helps! :)