Answer
$\qquad \kappa=0$
Work Step by Step
A formula that should have been included in the main text:
\[
\begin{array}{c}
\kappa=\frac{\left|\frac{d^{2} y}{d x^{2}}\right|}{\left(1+\left(\frac{d y}{d x}\right)^{2}\right)^{3 / 2}} \quad(E x \cdot 23.6 \text { ,Section } 12.5) \\
-\cos x=0 \text { at } x=\pi / 2 \text { , }=\qquad \frac{d^{2} y}{d x^{2}} \\
\end{array}
\]
