1. ## Related Rates problem

An aircraft is flying at a constant altitude with a constant speed of 600 mi/hr. An antiaircraft missile is fire on a straight line to the flight path of the aircraft so that it will hit the aircraft at point P. Suppose that the angle between the flight paths from point P is 120 degrees. At the instant the aircraft is 2 miles from the impact point P, the missile is 4 miles from P and flying at 1200 mi/hr. At that instant, how rapidly is the distance between the missile and the aircraft decreasing?

I think that I need to use the law of cosines.

2. Yes that is correct.

All you have to do is use the law of cosines to find out what the distance between the plane and missile is when they are 2 and 4 miles away, respectively, from point P, then you just need to differentiate the law of cosines, plug everything in, and solve!

3. Thanx a lot. I got an answer that seems correct. I used 30-60-90 triangle relationships to get a value for the hypotenuse

4. But it's not a 30-60-90 triangle...