8.
如图,在△ABC中,AC=BC=4,将线段AB绕点A逆时针旋转90°,连接CD,则线段CD的最小值是( )
| A. | $\sqrt{2}$ | B. | 2 | C. | 2$\sqrt{2}$-2 | D. | 4$\sqrt{2}$-4 |
2.
如图,点E(x1,y1),F(x2,y2)在抛物线y=ax2+bx+c上,且在该抛物线对称轴的同侧(点E在点F的左侧),过点E、F分别作x轴的垂线,分别交x轴于点B、D,交直线y=2ax+b于点A、C.设S为四边形ABDC的面积.则下列关系正确的是( )
| A. | S=y2+y1 | B. | S=y2+2y1 | C. | S=y2-y1 | D. | S=y2-2y1 |
19.
如图,△ABC内接于⊙O,⊙O的半径为5,sin∠B=$\frac{3}{5}$,点D在边AC上,在弧BC上取一点E.使得∠CDE=∠ABC.且AE=$\sqrt{3}$DE.则CD的长为( )
0 297111 297119 297125 297129 297135 297137 297141 297147 297149 297155 297161 297165 297167 297171 297177 297179 297185 297189 297191 297195 297197 297201 297203 297205 297206 297207 297209 297210 297211 297213 297215 297219 297221 297225 297227 297231 297237 297239 297245 297249 297251 297255 297261 297267 297269 297275 297279 297281 297287 297291 297297 297305 366461
| A. | 2$\sqrt{2}$ | B. | 2 | C. | $\sqrt{3}$ | D. | 2.5 |