Posted by Jordan on Thursday, November 11, 2010 at 3:42pm.
A plane flying horizontally at an altitude of 3 mi and a speed of 480 mi/h passes directly over a radar station. Find the rate at which the distance from the plane to the station is increasing when it is 6 mi away from the station. (Round to the nearest whole number.)

Cal  MathMate, Thursday, November 11, 2010 at 4:20pm
Use Pythagoras theorem.
x=horizontal distance from station
L(x)=oblique distance from station
L(x)=√(480²+x²)
dx/dt = horizontal speed = 480 mph
Find dL(x)/dx by differentiation.
Then
dL(x)/dt
= dL(x)/dx * dx/dt 
Cal  Anyomous, Thursday, November 11, 2010 at 6:31pm
that makes no sense