17.
如图,在正方形ABCD中,AC为对角线,点E在AB边上,EF⊥AC于点F,连接EC,AF=3,△EFC的周长为12,则EC的长为( )
| A. | $\frac{7\sqrt{2}}{2}$ | B. | 3$\sqrt{2}$ | C. | 5 | D. | 6 |
16.下列说法错误的是( )
| A. | 斜边及一锐角分别相等的两个直角三角形全等 | |
| B. | 两条直角边分别相等的两个直角三角形全等 | |
| C. | 两个锐角分别相等的两个直角三角形全等 | |
| D. | 一条直角边相等且另一条直角边上的中线相等的两个直角三角形全等 |
15.等边三角形两条中线相交所成的锐角的度数为( )
0 294127 294135 294141 294145 294151 294153 294157 294163 294165 294171 294177 294181 294183 294187 294193 294195 294201 294205 294207 294211 294213 294217 294219 294221 294222 294223 294225 294226 294227 294229 294231 294235 294237 294241 294243 294247 294253 294255 294261 294265 294267 294271 294277 294283 294285 294291 294295 294297 294303 294307 294313 294321 366461
| A. | 30° | B. | 45° | C. | 60° | D. | 75° |