题干

某市开展一项自行车旅游活动,线路需经A、B、C、D四地,如图,其中A、B、C三地在同一直线上,D地在A地北偏东30°方向,在C地北偏西45°方向,C地在A地北偏东75°方向.且BC=CD=20km,问沿上述线路从A地到D地的路程大约是多少?(最后结果保留整数,参考数据:sin15°≈0.25,cos15°≈0.97,tan15°≈0.27, 21.4,31.7
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答案(点此获取答案解析)

解:由题意可知∠DCA=180°﹣75°﹣45°=60°,

∵BC=CD,

∴△BCD是等边三角形.

过点B作BE⊥AD,垂足为E,如图所示:

同类题5

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    The GRAMMY Museum is a musically fascinating journey of music in downtown Los Angeles. Turn up the beat over four floors of modern exhibits, interactive(互动的) experiences and interesting films that will give you a one-of-a-kind experience. They want to engage you, educate you, and inspire you — just like music does!

    There are over 30,000 square feet of interactive, traveling and permanent (永久的) exhibits. This includes over two dozen exhibits along that explore the greatest of the GRAMMY music! Your whole family will find something they love — rock, classical, hip hop to country…

    The Crossroads exhibition invites you to explore nearly 160 kinds of music! Open them up on the interactive table in front of you to show photos, songs and stories that describe the influence that music has on the world, as well as the music itself.

    Journey down the Songwriters Hall of Fame. How many of these songs do you know? How many songwriters have you heard of? You can also try writing a song with some songwriters in the songwriting kiosks(自助式服务设备)!

    Have you wondered how a song gets from someone's head to your radio? The third floor shows the art of recording.

    The museum always has a host of programs and events throughout the year, so make sure you keep up to date — you won't want to miss out!

HOW MUCH DOES IT COST?

Adults: $ 12.95

Children: $ 10.95 (6-17 yrs)

Free: under 5 years old

WHEN CAN WE GO?

Mon-Fri: 11:30 am – 7:30 pm

Weekends: 10:00 am – 7:30 pm

    Sometimes shut for private events, so check before you go.