题干

如图,大楼底右侧有一障碍物,在障碍物的旁边有一幢小楼DE,在小楼的顶端D处测得障碍物边缘点C的俯角为30°,测得大楼顶端A的仰角为45°(点B,C,E在同一水平直线上).已知AB=80m,DE=10m,求障碍物B,C两点间的距离.(结果保留根号)

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答案(点此获取答案解析)

解:如图,过点D作DF⊥AB于点F,过点C作CH⊥DF于点H.

则DE=BF=CH=10m,

同类题2

阅读下面短文,从短文后各题所给的A、B、C和D四个选项中,故答案选出可以填入空白处的最佳选项。

    Easter is a holiday celebrated all over the world. A lot of people like to do 1 things during the Easter weekend. One year my friends Katherine and David decided to 2 on the weekend. They lived in Houston and I lived in San Antonio, about 250km away.

    I was very 3 to go to the wedding. I 4 a new black suit, new black shoes, and a great wedding gift for Katherine and David. After having breakfast in my apartment, I was ready to go and got into my car. I started the car and was 5! The car made a very loud scratchy 6. It didn't start. My car was 7!

    I 8 called my other friends who were going to the wedding. They were all in Houston already. I was so 9. I really wanted to go to the wedding. Then I 10 one more person that might still be in San Antonio. The girl I 11, Emily.

    I called Emily to see if she was still in town and she was! She came to my 12 and we drove to the wedding together. I was a little nervous 13 I liked her very much, but I didn't dare to ask her out. On the way, we had a great14 and we were both really excited for David and Katherine and couldn't 15 to get there.

    The wedding was beautiful. There was so much delicious food at the16, and because it was Easter, the entire wedding was 17 in very bright colors. The best part was that Emily and I danced all night together. I got to know her very well and we decided to go on a 18 when we 19 to San Antonio. My car breaking down was the best thing that 20 to me that Easter weekend!