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问题 解答题
已知tanα=3，求值
（1）
4sinα-2cosα
3sinα+5cosα

（2）2sin2α+sinαcosα-3cos2α
答案

（1）将原式分子分母同时除以cosα，

原式=

4tanα-2
3tanα+5
=
5
7

（2）将原式分子分母同时除以cosα，化为关于tanα的三角式，代入求解即可

原式=

2sin2α+sinαcosα-3cos2α
sin2α+cos2α
=
2tan2α+tanα-3
tan2α+1
=
9
5

单项选择题

货币贬值改善国际收支的条件是（）

A、Dx+Di=1

B、Dx+Di>1

C、Dx+Di<1

D、Dx－Di>1
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单项选择题

Many students have hobbies, such as reading, painting, growing vegetables in their gardens, and looking after animals. Some hobbies are relaxing and (16) are creative. Hobbies can develop your interests and help you learn new skills.
David Smith is a student, and his hobby is writing. (17) the sumer of 2000, he spent four weeks on a summer camp. As well as the usual activities, such as sailing, climbing and mountain biking, there was a writing workshop with a professional (18) "She asked us to imagine that we were in a story. Then we wrote about our (19) at the camp. "
In senior high school David wrote a story about teenage life, and it (20) as a book in 2003. Many teenagers love his book, and as a result, David has become a (21) young writer.
David has been very lucky (22) his hobby has brought him enjoyment and success, but he is (23) interested in many other things. "I like playing volleyball, too" says David. "I spend some of my free time playing volleyball for my school team. (24) I’ll write more books in the future, but I’m not sure. "
It’s sometimes difficult (25) that we shouldn’t spend all our time on our favourite hobby. There are many other interesting things to do in life, and we should try to do something new or different.

Ⅱ. 完形填空/Cloze

A．Usually

B．Immediately

C．Maybe

D．Once
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