题干

已知三棱柱ABC-A1B1C1的侧棱与底面垂直,体积为
9
4
,底面是边长为3的正三角形,若P为底面A1B1C1的中心,则PA与平面ABC所成角的大小为(    )

A:5π12

B:π3

C:π4

D:π6

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B

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    A couple of weeks ago, a few friends and I had an opportunity to attend a dear friend's wedding in New York. After the wedding and reception, rather accidentally four of us gathered in a hotel room and began to explore the deeper meaning of life and death. What does it mean to live truly? If we are all getting closer to death, is all the material accumulation worth it? It is not exactly the type of conversations one has at a wedding.

    While the answers varied from person to person, I was left with more questions than answers and a feeling of gratefulness to be surrounded by friends who were asking the “right” questions. As the clock kept ticking past 3 a.m., one of the roommates suggested we watch a short film titled “Last Days of Zach Sobiech”. The film is about a teenager's journey through the last days of his incurable illness. The film brought up a lot of mixed emotions but one quote that stood out for me was Zach's simple explanation of happiness, “What makes one happy is seeing someone else smile because you put it there.” By 4 a.m. , there was this energy in the room that had to be shared! With a few packages of post-it notes, we hit the halls of the hotel. We decided to leave short inspirational words on guests' doors, so when they opened their doors few hours later a smile would turn up.

    We ended up sticking post-it notes on all the doors until we ran out of them. The note on the door of the newly-weds properly said, “Where there is love, there is life.”