00:01
So we write the vector negative 25.
00:06
So that you can write as negative 8 i minus 11 j to write that.
00:41
It is 8 i minus 6 j and f is 4 i 11 j.
00:53
And we're trying to find 5f plus 2 e.
00:57
So we have to take 5 times f and 2 times e.
01:01
So that is 16 i of j.
01:06
We're adding 20 plus 55 which 16 and 20 is 36i plus 3 j find the direction angle of 3 plus 2 j 3 i plus 2 j 3 1 2 j that's that vector right there this is 3 that's 2 and we want to find this angle here so we can say tangent of theta and here inverse tangent of 2 divided by 3 33 now if your vector happens to be in a different quadrant let's say it is here and this is 4 and that is 5 well you can still figure it out by saying inverse tangent would be 5 4s then you have to just understand what vector you're in or what quadrant you're in.
03:01
So inverse tangent of five force is 51 .3 degrees.
03:09
0 .34.
03:11
If we want to know the direction angle we're talking about an angle that starts here and goes there.
03:18
So it's not 51 .34.
03:22
It's 180 minus that and so that would be a 128 .66 and then it might if your vector was down here, still do the same thing.
03:41
Take the inverse tangent of this over that.
03:43
Get an angle.
03:45
But now you're talking this vector that goes all the way from there to there.
03:49
So now you'd have to take 180 plus whatever angle you got.
03:53
And then if you're in this quadrant here, and you're figuring it out to you figure out this angle and take the inverse tangent of that over that.
04:02
And then you have that angle, but now you'd have to take 360 minus whatever that angle is to get this one.
04:16
Yeah, that's what you should do that.
04:18
All right, 2 .6 and a negative 3, 4.
04:27
And figure out the angle between that...