2011-II-16

20-06-2023 app.cch 尚無留言

答案：C
設

θ

為該扇形的圓心角，則可得

$\begin{array}{rcl} π (12)^{2} \times \frac{θ}{360^{\circ}} & = & 48 π \\ θ & = & 120^{\circ} \end{array}$

所以，該扇形的周界

$\begin{array}{cl} = & 2 π (12) \times \frac{120^{\circ}}{360^{\circ}} + 2 (12) \\ = & 49.132 741 23 \\ \approx & 49.1 cm \end{array}$