Answer
$\frac{1}{2 \sqrt{2}}$
Work Step by Step
A formula that should have been included in the main text:
\[
\begin{array}{c}
\kappa=\frac{\left|\frac{d^{2} y}{d x^{2}}\right|}{\left(1+\left(\frac{d y}{d x}\right)^{2}\right)^{3 / 2}} \quad(E x .23 .6, \text { Section 12.5 }) \\
\qquad \begin{array}{l}
\frac{d y}{d x}=1 / x \\
\frac{d^{2} y}{d x^{2}}=-1 / x^{2} \\
\frac{1}{2^{3 / 2}}=\frac{1}{2 \sqrt{2}}=\qquad \kappa(1)
\end{array}
\end{array}
\]
