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**calc_student09** A rectangle has a constant area of 200 square meters and its length L is increasing at the rate of 4 meters per second

1)Find the width W at the instant the width is decreasing at the rate of .5 meters per second.

2) At what rate is the diagonal D of the rectangle changing at the instant when the width W is 10 meters?

1)So I know that DL/Dt= 4 and Dw/dt= -.5

So the equation is A=LW, the derivative being Da/dt= L(dw/dt)+W(dL/dt)

Would that be 0=L(-.5)+W(4)

What would I do next there?

you know LW = 200 ...

2)How would I start this one off?

how about D^2 = L^2 + W^2 ?