## University Calculus: Early Transcendentals (3rd Edition)

change in diameter = $\frac{2}{\pi}$ change in cross section = $10\ in^2$
The given change in circumference of a tree: (dC)=2 We need to find the change in diameter (dD) circumference(c)=$\pi d$ change in circumference $(dC)=\pi dD$ so $2=\pi dD$ and $dD=\frac{2}{\pi}$ change in cross-sectional area, diameter(D)=10in. area(A)=$\pi r^2=\pi {\frac{D^2}{4}}$ change in cross section (dA) = $\frac{2\pi}{4}DdD=\frac{2\pi\times2\times10}{4\pi}=10in^2$ Thus, the final answer is: change in diameter = $\frac{2}{\pi}$ change in cross section = $10\ in^2$