Question
A stone is dropped into a quiet lake and waves move in circles at the speed of $5 \mathrm{~cm} / \mathrm{s}$. At the instant when the radius of the circular wave is $8 \mathrm{~cm}$, how fast is the enclosed area increasing?
Step 1
We are given that the radius is increasing at a rate of $5 \, \text{cm/s}$, so we can write this as $\frac{dx}{dt} = 5$. Show more…
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