calculus 1
posted by cindy .
I just need help getting started. I can't figure out the equation I need to use!
An airplane passes over an airport at noon traveling 500 mi/hr due
West. At 1:00 pm, another airplane passes over the same airport at the same
elevation traveling due North at 550 mi/hr. Assuming both planes maintain their
(equal) elevations, how fast is the distance between them changing at 2:30 pm?

draw the figure, and start with the pythoragus theorem.

Ok so I figured the equation out but after I took the derivative I wasn't sure what to plug in where