Question

如图，小明在楼上点A处观察旗杆BC，测得旗杆顶部B的仰角为30°，测得旗杆底部C的俯角为60°，已知点A距地面的高AD为12m．求旗杆的高度．

                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                             

                                                                                                                                                             

答案：

Answer 1

解：过点A作AE⊥BC，垂足为E，得矩形ADCE，∴CE=AD=12.

Rt△ACE中，∵∠EAC=60°，CE=12，

∴AE=.       

Rt△ABE中，∵∠BAE=30°，BE=AE.

∴BC=CE+BE=16m.