如图,AB为⊙O的直径,点C,D在⊙O上.若∠AOD=30°,则∠BCD的度数是 °
如图,AB为⊙O的直径,点C,D在⊙O上.若∠AOD=30°,则∠BCD的度数是°....
如图,AB为⊙O的直径,点C,D在⊙O上.若∠AOD=30°,则∠BCD的度数是 °.
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东子oSA
推荐于2017-12-16
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试题分析:AB为⊙O的直径,点C,D在⊙O上,∠BCD= ![](https://iknow-pic.cdn.bcebos.com/5d6034a85edf8db1d7ce36d60a23dd54574e749b?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) ,因为 ![](https://iknow-pic.cdn.bcebos.com/8cb1cb1349540923c28929cc9158d109b2de499b?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) 是直径AB所对的圆周角,所以 ![](https://iknow-pic.cdn.bcebos.com/8cb1cb1349540923c28929cc9158d109b2de499b?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) = ![](https://iknow-pic.cdn.bcebos.com/ca1349540923dd547693eddad209b3de9d82489b?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) ,∠AOD, ![](https://iknow-pic.cdn.bcebos.com/48540923dd54564eb385ae8bb0de9c82d0584f9b?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) 是弧AD所对的圆心角和圆周角,∠AOD=30°,所以 ![](https://iknow-pic.cdn.bcebos.com/9f510fb30f2442a7bfc8b717d243ad4bd01302b9?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) ,所以∠BCD= ![](https://iknow-pic.cdn.bcebos.com/43a7d933c895d143c4b0ae9170f082025baf07b9?x-bce-process=image%2Fresize%2Cm_lfit%2Cw_600%2Ch_800%2Climit_1%2Fquality%2Cq_85%2Fformat%2Cf_auto) =105° 点评:本题考查圆心角和圆周角,解答本题的关键是掌握圆中圆心角和圆周角的概念和同弧所对的圆心角和圆周角之间的关系 |
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