00:01
I'm going to draw a diagram of what's going on here.
00:04
We've got two cars.
00:05
One is driving south and going away from an intersection.
00:10
And the other one is going toward the intersection and moving west.
00:18
So i have trouble drawing points on here.
00:30
So i'm going to call that the intersection.
00:34
South away from the intersection.
00:37
So this will be car a, and then car b is moving to the west toward the intersection.
00:57
I don't know why things disappear here.
01:01
Okay.
01:02
Again, it makes a triangle, just like in the previous question, and i'm going to call this x, and i'm going to call this y.
01:17
And so, oh, i'm also going to call that l.
01:23
So l squared equals x squared plus y squared, according to the pythagorean theorem.
01:31
I'll take the derivative with respect to time.
01:35
2l, dl over dt equals 2x, dx over dt, 2y, dx over dt, 2y, d -y over d -t.
01:55
Now let's see if we have all the information we need...