00:01
In this exercise, we have two vectors a and b, and we have c that is just the sum of these two vectors.
00:09
So c equals a plus b.
00:12
In question a, we have to show that if c squared is equal to a squared plus b squared, then the angle theta between a and b is equal to 90 degrees.
00:27
So notice that c squared is equal to the dot product between c.
00:31
In itself.
00:35
And since c is equal to a plus b, we have that this is the dot product between a plus b and a plus b.
00:44
So this is a.
00:46
Dot a plus b plus b dot b plus two times a.
00:53
B.
00:56
Now, a.
00:57
Dot a is a squared.
00:59
B that b is b squared.
01:01
And a .b is ab times a cosine of the angle between the two.
01:07
Now let's impose that c squared is equal to a squared plus b squared.
01:14
This means that the a square and b squared cancels out...