【简答题】听力原文:Welcome to our series on renewable resources. The topic today is hydropower. As you most probably know, 'hydro' means water—so we are talking about using water to generate electricity. Of course,...
【简答题】已知:直线AB和点C的投影,且水平线DC⊥AB,DC长40mm(图2-5a)。 求作:线段DC的投影。
【单选题】The natural resources, such as mine, forest, and hydropower (水电) in that area have been ________. [ ]
【简答题】如图,AB是⊙ 的直径,弦CD与AB交于点E,过点 作⊙ 的切线与 的延长线交于点 ,如果 , , 为 的中点. (1)求证: ; (2)求AB的长.