题目

已知PA⊥平面ABC，∠ABC＝１２0°，0A＝AB＝BC＝６，则PC等于(　　)A.6                               B.6                       C.12                                   D.144 答案：解析:∵,∴＝36＋36＋36＋2×36cos60°＝144.∴｜PC｜＝12.答案:C

查看本题答案和解析