미분 방정식 $y''+16y= \delta (t-2 \pi), y (0) =0, y' (0) =0$ 의 해는?

• ①$\displaystyle \frac{1} {4} \sin (4t) u (t+2 \pi)$
• ②$\displaystyle \frac{1} {4} \cos (4t) u (t-2 \pi)$
• ③$\displaystyle \frac{1} {4} \cos (4t) u (t+2 \pi)$
• ④$\displaystyle \frac{1} {4} \sin (4t) u (t-2 \pi)$