\[d = \ 16\ см:\]
\[a_{4} = 2R_{4}\sin\frac{180{^\circ}}{4} =\]
\[= 2 \bullet \frac{16}{2} \bullet \sin{45{^\circ}} = 16 \bullet \frac{\sqrt{2}}{2} =\]
\[= 8\sqrt{2} = \sqrt{8^{2} \bullet 2} = \sqrt{128}\ см.\]
\[12 = \sqrt{12^{2}} = \sqrt{144} > \sqrt{128}.\]
\[Ответ:\ \ нет.\]