posted by fareha .
1. A rectangle has a constant area of 200 square meters and its length L is increasing at the rate of 4 meters per second.
a. Find the width W at the instant the width is decreasing at the rate of .4 meters per second.
b. At what rate is the diagonal D of the rectangle changing at the instant when the width W is 10 meters?
l dw/dt+ W dl/dt=0
a) find w then dw/dt=-.4
but remember LW=200 or L=200/W
solve for W
b. diagonal D.
dD/dt= 1/2 *1/sqrt( ) * (2L dl/dt+ 2W dw/dt)