Posted by Anonymous on .
A jogger runs around a circular track of radius 65 ft. Let (x,y) be her coordinates, where the origin is the center of the track. When the jogger's coordinates are (39, 52), her x coordinate is changing at a rate of 15ft/s. Find (dy/dx)

Calculus 
Reiny,
I think you want to find dy/dt
or else we don't need the fact that
dx/dt = 15 ft/s
x^2 + y^2 = 65^2
2x dx/dt + 2y dy/dx= 0
dy/dx = (2x dx/dt)/(2y) = (x dx/dt)/y
so for the given data
dy/dt = 39(15)/52 = 45/4 or 11.25 ft/s