ans
012287
$\{-1,0,1\}$

012288
$\pi$

012289
$3+4\mathrm{i}$

012290
$2$

012291
$1$

012292
$16\pi$

012293
$(-\dfrac 15,\dfrac 25)$

012294
$[-1,\dfrac 12]$

012295
$(4,5]$

012296
$y=\pm 2\sqrt{2} x$

012297
$\dfrac{5\sqrt{3}}6\pi$

012298
$(0,2)$, $-6$

012299
B

012300
C

012301
A

012302
A

012303
(1) 证明略; (2) $\arccos \dfrac{\sqrt{5}}3$

012304
(1) $\dfrac\pi 3$; (2) $2\sqrt{3}+2$

012305
(1) $120$米; (2) $20$米时, 总造价最低

012306
(1) $\dfrac{x^2}3+y^2=1$; (2) $\dfrac 12$; (3) $2$

012307
(1) $f(x)=\mathrm{e}^{x+1}$; (2) $g(n)=\begin{cases}\dfrac{3n-1}{2}, & n\text{为奇数},\\ \dfrac{3n-2}{2}, & n\text{为偶数};\end{cases}$ (3) 存在``阈度'', 取值范围为$[\dfrac{\mathrm{e}^4+1}{\mathrm{e}^4-\mathrm{e}},+\infty)$

012308
$\{2,3,4\}$

012309
$(-\dfrac 12,2)$

012310
$6$

012311
$2$

012312
$-8$

012313
$-4$

012314
$\dfrac 12$

012315
$\sqrt{3}$

012316
$y=2x-1$

012317
$2$

012318
$[-4,12]$

012319
$2+\sqrt{3}$

012320
D

012321
A

012322
B

012323
A

012324
(1) $\dfrac 43$; (2) $\arccos \dfrac{\sqrt{6}}6$

012325
(1) $[k\pi-\dfrac{3\pi}8,k\pi+\dfrac\pi 8]$($k\in \mathbf{Z}$); (2) $[-\dfrac{\sqrt{2}}2,\dfrac{\sqrt{2}}2]$

012326
(1) $y=-0.02x^2+100$($0\le x\le 50$); (2) $f(x)=\begin{cases}x(-0.02x^2+100), & 30\le x\le 50, \\ x(-x+100), & 50<x\le 70;\end{cases}$ (3) 当点$D$在曲线段$BC$上且其到$OA$的距离约为$66.7$米时, 游乐场的面积$S$最大

012327
(1) $\dfrac{x^2}{\frac{1+\sqrt{5}}2}+y^2=1$; (2) $\dfrac{4+2\sqrt{3}}5$; (3) 相切, 证明略

012328
(1) $[4,+\infty)$; (2) 证明略; (3) $4$或$5$