A ladder 20 feet long leans against a house. Find the rate at which the top of the ladder is moving
downward if the foot of the ladder is 12 feet away from the house and sliding along the ground away
from the house at the rate of 2 feet per second?
If x is the distance from the wall
and y is the height up the wall, then
when x=12, y=16
x^2 + y^2 = 20^2
x dx/dt + y dy/dt = 0
12*2 + 16 dy/dt = 0
dy/dt = -3/2 ft/s