①AD是∠BAC的平分线；②∠ADC=60°；③点D在AB的中垂线上；④S_△DAC：S_△ABC=

1：3．

    ____crowd of more than 22,000 people gathered near Las Vegas' famous Mandalay Bay Hotel____the Route 91 Harvest Festival. Without____(expect), from the hotel's 32^nd floor, a gunman opened fire on the people below,____ (kill)59 people and at least 500 injured. It was the most____(dead)shooting in US history. President Donald Trump described____as “an act of pure evil”. He ordered US flags to be____(fly)at half-staff to honor those____died. “In moments of tragedy and horror, America comes together as one. And it always ____(have),” Trump said____(Politician) around the world offered their support for the United States.

一个零件的实际长度是3毫米，画在一幅图上长1.5厘米，这幅图的比例尺是（  ）

如图，在▱ABCD中，点E在BC边上，且AE⊥BC于点E，ED平分∠CDA，若BE：EC=1：2，则∠BCD的度数为____ 

正三棱柱$ABC-A_1{B}_1{C}_{}$中，$AB=A{A}_1$则$A{C}_1$与平面$B{B}_1{C}_{1}C$所成角的正弦值为（   ）