1/5单选题
难度：
1.已知PA是⊙O的切线，A为切点，PBC是过点O的割线，PA=10cm，PB=5cm，则⊙O的半径长为（ ）
| A | 15cm |
| B | 10cm |
| C | 7.5cm |
| D | 5cm |
- 提示1：
- IOagueaNrue7k+iuulBBPHN1cD4yPC9zdXA+PVBPJiM4MjI2O1BD5b6X5Ye6
正确答案：Qw==
6Kej77ya5qC55o2uUEE8c3VwPjI8L3N1cD49UE8mIzgyMjY7UEPvvIw8YnI+5omA5LulMTAwPTXDl1BD77yMUEM9MjBjbe+8jEJDPTIwLTU9MTVjbS4gPGJyPuWboOS4ulBCQ+aYr+i/h+eCuU/nmoTlibLnur/vvIw8YnI+5omA5Lul4oqZT+eahOWNiuW+hOmVv+S4ujE1w5c8aW1nIHdpZHRoPTggaGVpZ2h0PTQyIHNyYz0iaHR0cHM6Ly9wMS5xaW5nZ3VvLmNvbS9HMS9NMDAvQjQvMDMvckJBQ0UxUGtpbU9qaWp6bEFBQUJEblY0UlFZOTc1LnBuZyI+PTcuNWNtLiA8YnI+5pWF6YCJQ+OAgg==
2/5单选题
难度：
2.
如图⊙O的两条弦AB、CD相交于点E，AC与DB的延长线交于点P，下列结论中成立的是（ ）
| A | CE•CD=BE•BA |
| B | CE•AE=BE•DE |
| C | PC•CA=PB•BD |
| D | PC•PA=PB•PD |
- 提示1：
- PHA+5LiJ6KeS5b2iUEJB5LiO5LiJ6KeS5b2iUENE55u45Ly8PC9wPg==
正确答案：RA==
PHA+6Kej77ya55Sx4oigUD3iiKBQ77yM4oigQT3iiKBE77yM5Y+v5b6X5LiJ6KeS5b2iUEJB5LiO5LiJ6KeS5b2iUENE55u45Ly8PGJyPuKItFBCOlBDPVBBOlBEPGJyPuKItFBD4oCiUEE9UELigKJQRDxicj7mlYXpgIlE44CCPC9wPg==
3/5单选题
难度：
3.
如图，从圆O外一点P引圆O的割线PAB和PCD，PCD过圆心O，已知PA=1，AB=2，PO=3，则圆O的半径等于（ ）
| A |
|
| B |
|
| C |
|
| D |
|
- 提示1：
- PHA+55Sx5LqOUEFC5LiOUENE5piv5ZyG55qE5Lik5p2h5Ymy57q/77yM5LiUUEE9Me+8jEFCPTLvvIxQTz0z77yM5oiR5Lus5Y+v5Lul6K6+5ZyG55qE5Y2K5b6E5Li6Uu+8jOeEtuWQjuagueaNruebuOS8vOe7k+iuuuaehOmAoOS4gOS4quWFs+S6jlLnmoTmlrnnqIvvvIzop6PmlrnnqIvljbPlj6/msYLop6MuPC9wPg==
正确答案：Qw==
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
4/5单选题
难度：
4.
已知如图，AB、AC分别是⊙O的直径和切线，BC交⊙O于D. AB=8，AC=6，则CD的长为（ ）
| A | 3 |
| B | 4 |
| C | 9 |
| D | 3.6 |
- 提示1：
- PHA+5YWI6L+e5o6lQUTvvIznlLHkuo5BQuaYr+ebtOW+hO+8jEFD5piv5YiH57q/77yM6YKj5LmI5Y+v55+l4oigQURCPTkwwrDvvIziiKBDQUI9OTDCsO+8jOWcqFJ04pazQUJD5Lit5Yip55So5Yu+6IKh5a6a55CG5piT5rGCQkPvvIzogIziiKBBQkQ94oigQ0JB77yM4oigQURCPeKIoENBQu+8jOaYk+ivgeKWs0FCROKIveKWs0NCQe+8jOWIqeeUqOavlOS+i+e6v+auteWPr+axgkJE77yM6L+b6ICM5Y+v5rGCQ0QuPC9wPg==
正确答案：RA==
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
5/5单选题
难度：
5.
已知⊙O的割线PAB交⊙OA，B两点，割线PCD经过圆心，若PA=3，AB=4，PO=5，则⊙O的半径为（）
| A | 2 |
| B | 2.4 |
| C | 3 |
| D | 3.6 |
- 提示1：
- PHA+55Sx5LqOUEFC5LiOUENE5piv5ZyG55qE5Lik5p2h5Ymy57q/77yM5LiUUEE9M++8jEFCPTTvvIxQTz0177yM5oiR5Lus5Y+v5Lul6K6+5ZyG55qE5Y2K5b6E5Li6Uu+8jOeEtuWQjuebuOS8vOe7k+iuuuaehOmAoOS4gOS4quWFs+S6jlLnmoTmlrnnqIvvvIzop6PmlrnnqIvljbPlj6/msYLop6MuPC9wPg==
正确答案：QQ==
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