00:01
In this problem, we have an airplane flying towards an airport.
00:05
It is currently 40 miles away from the airport.
00:10
The rate at which the distance between the airplane and the airport is changing is negative 240 miles per hour.
00:19
What we are asked to find is the speed or the rate at which the speed is changing if the height is 4 miles.
00:29
So i've drawn a model of the situation and we can see that we have a right triangle.
00:37
So we will be utilizing the pythagorean theorem.
00:42
So based on our triangle, we have here that x squared plus h squared is equal to squared.
01:01
Now we need to take the derivative of this.
01:06
If i do, x and x and s are functions of time.
01:12
So what we have here is 2x times x prime.
01:18
H is constant, so the derivative is zero, and that is equal to 2 s times s prime.
01:28
When we solve for x prime, what we get is that it's equal to s times s prime over x.
01:38
Now note we need both, we need to know x, s and s prime...