A ladder 10 feet long leans against a vertical building. If the bottom of the ladder slides away
from the building horizontally at a rate of 2 ft/s, how fast is the ladder sliding down from the
building when the ladder is 6 feet above the ground?

Question

A ladder 10 feet long leans against a vertical building. If the bottom of the ladder slides away
from the building horizontally at a rate of 2 ft/s, how fast is the ladder sliding down from the
building when the ladder is 6 feet above the ground?

anonymous · Answer

use pythagoras |dw:1413558006342:dw|

anonymous · Answer

x and y are related via 
$$x^2+y^2=100$$

anonymous · Answer

taking derivatives gives 
$$2yy'+2xx'=0$$ or$$yy'+xx'=0$$  you are told $y'=2$, solve for $x'$