00:01
In this problem we are given two vectors a and b and we are going to answer some questions about them.
00:08
Okay a is equal to 1, 2, minus 3 in this tuple notation and b is given by 3, minus 1 and 2.
00:20
Okay part a.
00:23
We define two vectors c and d as c equal to a plus b and d equal to a minus b.
00:34
We will show that c and d are perpendicular to each other.
00:39
Okay c can be found to be 4, 1, minus 1 and d is equal to minus 2, 3, minus 5.
00:52
So perpendicular means their dot product should be equal to 0.
00:57
So we have minus 8 plus 3 plus 5 which is equal to 0.
01:03
Therefore we say that c is perpendicular to d.
01:09
In the next part we are going to find a unit vector e which is perpendicular to both c and d.
01:25
Okay let's start with this general e vector and then we can normalize it later.
01:32
So i am going to indicate the components by e x, e y and e z.
01:38
So from the perpendicular relation with c we have e dot c equal to 0 and we also have e dot d equal to 0 with a similar reason.
01:55
Okay e dot c is 4, 4 e x, not exponential, plus e y minus e z.
02:06
And for the second dot product we have minus 2 e x plus 3 e y minus 5 e z.
02:15
From the first relation we can obtain e z equal to 4 e x plus e y and with that the second equation gives minus 11 e x.
02:31
So with that we obtain e z equal to minus 7 e x.
02:38
So we have this one free parameter to choose...