如图所示，某数学活动小组要测量山坡上的电线杆PQ的高度，他们在A处测得信号塔顶端P的仰角是45°，信号塔底端点Q的仰角为31°，沿水平地面向前走100米到B处，测得信号塔顶端P的仰角是68°，求信号塔PQ的高度．（结果精确到0.1米，参考数据：sin68°≈0.93，cos68°≈0.37，tan68°≈2.48，tan31°≈0.60，sin31°≈0.52，cos31°≈0.86）

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From:    annel@freemai14all.com    Sent: Wed., Oct. 19

To:      tss_liam@kidstarmail.net

Subject: Hello!

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Hi, Liam!

      So you're my new pen friend. Let me tell you a bit about myself. I'm 14 years old and I live in Calgary, CanadaI have two older brothers, Brian and Sam. I'm the only girl.

      I love sports and I'm always looking for exciting new hobbies to try. I like playing baseball in winter.

      It's fun beating the boys! But summer is my favourite time of the year. I love skateboarding and rock climbing in summer.

     Skateboarding's great because it's so fun and easy to learn! I often skateboard after school. There are many placesin the park where I can do stunts. I'm good at stunts like jumping and turning the skateboard!

     Rock climbing is also really fun. I usually climb with my dad on weekends. We can't do it on real mountains very often because we live in the city. We do indoor rock climbing instead but it's not as challenging.

    So that's me! How about you? Please write back soon!

Bye for now!

Anne