Question

（08年惠州一中三模理） 設函數

   （Ⅰ）求的最小正周期;

   （Ⅱ）在△ABC中，a，b，c分別是角A，B，C的對邊，

         求b，c的長.

Answer 1

解析：（Ⅰ）

                

                                                                      

              ∴                                                                                                                    

   （Ⅱ）f (A) = 2，    即                            

       

        ∴b² + c²－bc = 3                                          ①

        又b² + c² + 2bc = 9                                        ②

        ②－①      bc = 2                                    ③

b + c = 3                                             ④

b > c                                                   ⑤

解③④⑤得