Question

Related Rates: Two cars approach the intersection of two highways. The one coming from the west is traveling at 60mph and the one traveling from north is traveling at 50 mph. At what rate is the distance between the cars changing when the car from the west is 3 miles from the intersection and the car from the north is 4 miles from the intersection?
no ideas at all? Maybe the Pythagorean Theorem? The distance z is

z^2 = x^2+y^2
2z dz/dt = 2x dx/dt + 2y dy/dt
or
z dz/dt = x dx/dt + y dy/dt

Remembering your good old 3-4-5 right triangle, you can see that z=5 when x=3 and y=4.

Now, you have all the numbers you need to find dz/dt.
No I don't have any idea. And I had started out with the 3-4-5 triangle but didn't know what to do besides that

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