2.
如图,在△ABC中,∠BAC=90°,∠B=30°,AC=5cm,AD⊥BC于D,则BD=( )
| A. | 10cm | B. | 7.5cm | C. | 8.5cm | D. | 6.5cm |
1.在${\frac{1}{x}}、{\frac{1}{3}}、{\frac{{{x^2}+1}}{2}}、{\frac{5+y}{π}}、\frac{{{a^2}+1}}{a^2}$中分式的个数有( )
0 282150 282158 282164 282168 282174 282176 282180 282186 282188 282194 282200 282204 282206 282210 282216 282218 282224 282228 282230 282234 282236 282240 282242 282244 282245 282246 282248 282249 282250 282252 282254 282258 282260 282264 282266 282270 282276 282278 282284 282288 282290 282294 282300 282306 282308 282314 282318 282320 282326 282330 282336 282344 366461
| A. | 2个 | B. | 3个 | C. | 4个 | D. | 5个 |