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

問題詳情：

若tanα=2，則   =（　　）                                                                                   

A．                                B．                                C．                                D．

【回答】

B【分析】原式分子分母除以cosα，利用同角三角函數間基本關係化簡，將tanα的值代入計算即可求出值．                 

【解答】解：∵tanα=2，                                                                                    

∴原式===，                                                                           

故選：B．                                                                                                          

【點評】此題考查了同角三角函數基本關係的運用，熟練掌握基本關係是解本題的關鍵．                 

知識點：三角函數

題型：選擇題