函數(shù)在＝        處取得極小值．

在△ABC中，∠C＝900，AC＝4，則＝          。

已知方程在上有兩個不同的解，（＜），則下面結(jié)論正確的是 (　　)

A．                  B． 

C．                  D．

定義域為R的偶函數(shù)滿足對，都有成立，且當[2，3]時，．若函數(shù)在上至少有三個零點，則的取值范圍是（  ）

A．         B．        C．           D．

函數(shù)的圖象大致是(　　)

 設p、q是兩個命題，p ：＞0， q ：＞0，則p是q的（    ）

A．充分而不必要條件    B．必要而不充分條件     C．充要條件     D．既不充分也不必要條件

由曲線圍成的封閉圖形面積為 (　　)

A．           B．          C．                D．

設，，，則（    ）

A．a(chǎn)＜b＜c          B．b＜a＜c           C．b＜c＜a          D．a(chǎn)＜c＜b

數(shù)列的前項和為，若，則＝(　　)

A． 1                B．                 C．              D．

已知角的頂點與原點重合，始邊與x軸的正半軸重合，終邊在直線y ＝2 x上，則  （　　�。�                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                  

A．                B．               C.               D．