若tanα=2，则  =（　　）                                       ...

问题详情：

若tanα=2，则   =（　　）                                                                                   

A．                                B．                                C．                                D．

【回答】

B【分析】原式分子分母除以cosα，利用同角三角函数间基本关系化简，将tanα的值代入计算即可求出值．                 

【解答】解：∵tanα=2，                                                                                    

∴原式===，                                                                           

故选：B．                                                                                                          

【点评】此题考查了同角三角函数基本关系的运用，熟练掌握基本关系是解本题的关键．                 

知识点：三角函数

题型：选择题