1/5单选题
难度：
1.如图，AB是⊙O的切线，B为切点，AO与⊙O交于点C，若∠BAO=40°，则∠OCB的度数为（ ）
| A | 40° |
| B | 50° |
| C | 65° |
| D | 75° |
- 提示1：
- IOagueaNruWIh+e6v+eahOaAp+i0qOWPr+WIpOaWreKIoE9CQT05MMKw
- 提示2：
- IOWGjeeUseKIoEJBTz00MMKw5Y+v5b6X5Ye64oigTz01MMKw77yM5Zyo562J6IWw4pazT0JD5Lit5rGC5Ye64oigT0NC5Y2z5Y+vLg==
正确答案：Qw==
6Kej77ya4oi1QULmmK/iiplP55qE5YiH57q/77yMQuS4uuWIh+eCue+8jDxicj7iiLRPQuKKpUFC77yM5Y2z4oigT0JBPTkwwrDvvIw8YnI+4oi14oigQkFPPTQwwrDvvIw8YnI+4oi04oigTz01MMKw77yMPGJyPuKItU9CPU9D77yI6YO95piv5Y2K5b6E77yJ77yMPGJyPuKItOKIoE9DQj08aW1nIHdpZHRoPTYgaGVpZ2h0PTQyIHNyYz0iaHR0cHM6Ly9wMi5xaW5nZ3VvLmNvbS9HMS9NMDAvQTAvQjkvckJBQ0UxT1d1a21Td1FmekFBQUJISDAzcUV3NzYxLnBuZyI+77yIMTgwwrAt4oigT++8iT02NcKwLiA8YnI+5pWF6YCJQy4g
2/5单选题
难度：
2.如图，两个同心圆的半径分别为4cm和5cm，大圆的一条弦AB与小圆相切，则弦AB的长为（ ）
| A | 3cm |
| B | 4cm |
| C | 6cm |
| D | 8cm |
- 提示1：
- IOmmluWFiOi/nuaOpU9D77yMQU/vvIznlLHliIfnur/nmoTmgKfotKjvvIzlj6/lvpdPQ+KKpUFC77yM55Sx5Z6C5b6E5a6a55CG5Y+v5b6XQUI9MkFD
- 提示2：
- IOeEtuWQjueUseWLvuiCoeWumueQhuaxguW+l0FD55qE6ZW/77yM57un6ICM5Y+v5rGC5b6XQULnmoTplb8u
正确答案：Qw==
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
3/5单选题
难度：
3.如图，已知线段OA交⊙O于点B，且OB=AB，点P是⊙O上的一个动点，那么∠OAP的最大值是（ ）
| A | 90° |
| B | 60° |
| C | 45° |
| D | 30° |
- 提示1：
- IEFQ5LiO4oqZT+ebuOWIh+aXtu+8jOKIoE9BUOacieacgOWkp+WAvO+8jOi/nue7k09Q77yM5qC55o2u5YiH57q/55qE5oCn6LSo5b6XT1DiiqVBUO+8jOeUsU9CPUFC5b6XT0E9Mk9Q77yM54S25ZCO5qC55o2u5ZCrMzDluqbnmoTnm7Top5LkuInop5LlvaLkuInovrnnmoTlhbPns7vljbPlj6/lvpfliLDmraTml7biiKBPQVDnmoTluqbmlbAu
正确答案：RA==
6Kej77ya5b2TQVDkuI7iiplP55u45YiH5pe277yM4oigT0FQ5pyJ5pyA5aSn5YC877yM6L+e57uTT1DvvIzlpoLlm77vvIw8aW1nIHdpZHRoPTE0NSBoZWlnaHQ9MTA0IHNyYz0iaHR0cHM6Ly9wMS5xaW5nZ3VvLmNvbS9HMS9NMDAvNjQvOUMvckJBQ0ZGT1d1bEd3Ykh2ZUFBQVBMeC1lX1A4ODI1LnBuZyIgYWx0PemdkuaenOWtpumZoj48YnI+5YiZT1DiiqVBUO+8jDxicj7iiLVPQj1BQu+8jDxicj7iiLRPQT0yT1DvvIw8YnI+4oi04oigUEFPPTMwwrAuIDxicj7mlYXpgIlELiA=
4/5单选题
难度：
4.如图，以等边三角形ABC的BC边为直径画半圆，分别交AB、AC于点E、D，DF是圆的切线，过点F作BC的垂线交BC于点G. 若AF的长为2，则FG的长为（ ）
| A | 4 |
| B | 3 |
| C | 6 |
| D | 2 |
- 提示1：
- IOaOpU9E77yM55SxREbkuLrlnIbnmoTliIfnur/vvIzliKnnlKjliIfnur/nmoTmgKfotKjlvpfliLBPROWeguebtOS6jkRG77yM5qC55o2u5LiJ6KeS5b2iQUJD5Li6562J6L655LiJ6KeS5b2i77yM5Yip55So562J6L655LiJ6KeS5b2i55qE5oCn6LSo5b6X5Yiw5LiJ5p2h6L6555u4562J77yM5LiJ5YaF6KeS55u4562J77yM6YO95Li6NjDCsO+8jOeUsU9EPU9D77yM5b6X5Yiw5LiJ6KeS5b2iT0NE5Li6562J6L655LiJ6KeS5b2i
- 提示2：
- IE9E5bmz6KGM5LiOQULvvIznlLFP5Li6QkPnmoTkuK3ngrnvvIzlvpfliLBE5Li6QUPnmoTkuK3ngrnvvIzlnKjnm7Top5LkuInop5LlvaJBREbkuK3vvIzliKnnlKgzMMKw5omA5a+555qE55u06KeS6L65562J5LqO5pac6L6555qE5LiA5Y2K5rGC5Ye6QUTnmoTplb/vvIzov5vogIzmsYLlh7pBQ+eahOmVv++8jCDljbPkuLpBQueahOmVv++8jOeUsUFCLUFG5rGC5Ye6RkLnmoTplb/vvIzlnKjnm7Top5LkuInop5LlvaJGQkfkuK3vvIzliKnnlKgzMMKw5omA5a+555qE55u06KeS6L65562J5LqO5pac6L6555qE5LiA5Y2K5rGC5Ye6QkfnmoTplb/vvIzlho3liKnnlKjli77ogqHlrprnkIbljbPlj6/msYLlh7pGR+eahOmVvy4=
正确答案：Qg==
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
5/5单选题
难度：
5.如图，在等腰直角三角形ABC中，AB=AC=8，O为BC的中点，以O为圆心作半圆，使它与AB，AC都相切，切点分别为D，E，则⊙O的半径为（ ）
| A | 8 |
| B | 6 |
| C | 5 |
| D | 4 |
- 提示1：
- IOmmluWFiOi/nuaOpU9E77yM55Sx5YiH57q/55qE5oCn6LSo77yM5piT5b6XT0TiiqVBQu+8jOWNs+WPr+W+l09E5piv4pazQUJD55qE5Lit5L2N57q/77yM57un6ICM5rGC5b6XT0TnmoTplb8u
正确答案：RA==
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