00:01
Okay, now let's look at this problem.
00:01
Problem number 39.
00:04
Okay, so, sorry, problem number 37.
00:08
So we have two vectors, vector, two complex numbers, sorry.
00:13
One is z and the other one is w.
00:18
Okay, so we want to find z times w and the z over w.
00:28
Okay, so now let's find the, let's find the z first.
00:35
So z equals to two times cosine 2 pi over 9 actually equals to 77 over 100.
01:00
And sine pi over 2 equals to 17 over 50.
01:31
Okay, so which equals to 77 over 50 plus 17 over 25 times i.
01:47
Now let's find the value of w.
01:50
Okay.
01:51
W equals to 4 times cosine pi over 9.
02:01
Okay, so this actually equals to 94 over 100.
02:30
Or you can say that it is 47 over 50.
02:41
And sine i times sine pi over 9.
02:47
A sign of pi over 9 is actually 7.
03:09
So we have this equals to 94 over 25 plus i times 34 over 25.
03:38
Okay, now since we have z and w, so now let's find z times w.
03:44
Okay, actually there's an easy way that we can do this, so we can turn this z and w into the exponential form.
03:52
Okay, so we know this is r, this is theta.
03:55
So we have the exponential form is r times e to the theta i.
04:05
Okay, so which equals to two times e to the two pi minus nine times i.
04:12
And w we also have, we also can turn this into the exponential form, which equals to four times, okay, this is this is theta, okay...