If z^2 = x^2 + y^2 with z>0, dx/dt=3, and dy/dt=6, find dz/dt when x=4 and y=3.

Answer: \displaystyle \frac{dz}{dt} =

1 answer

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

when x=4 and y = 3
z^2 = 4^2 + 3^2 = 25
z = 5

Now that you have 5 of the 6 terms, just sub those in and solve for dz/dt