问题 选择题
我舰在敌岛A南偏西50°方向相距12海里的B处发现敌舰正由A离沿北偏西10°的方向以10海里/时的速度航行,我舰要沿直线用2小时追上敌舰,则需速度为(  )
A.13海里/时B.14海里/时C.2
19
海里/时
D.
31
海里/时
答案

解:如图所示:依题意可得,∠BAC=120°,AB=12,AC=10×2=20,

在△ABC中,由余弦定理,

得BC2=AB2+AC2-2AB×AC×cos∠BAC=122+202-2×12×20×cos120°=784.

解得BC=28.

所以我舰的速度为  =14海里/小时.

故选B.

阅读理解

     A quarrel at home may result in you falling ill. Don't laugh, it's true. Family matters including living

habits and even the way we speak have a big effect on our health, doctors say.

     Wang Xiaoyu, a Senior 2 girl from Xichang, Sichuan Province, fainted (晕倒) in class when she heard her classmates quarrel at the top of their voices. Quarrels between her parents also put the girl into a

coma. It is because she is suffering from depression (抑郁症), caused by bad relations at home, doctors

explained.

     "We don't get sick or stay well by ourselves," says Dr Robert Ferrer from the US. Ferrer shows that

family forces may explain up to a quarter of health problems, in his recent research. The genes you get

from your family may cause illness. If one of your parents has a heart attack, your risk of being affected

may double. But effects on health are not only written in our DNA.

     Unrelated people who live under the same roof also get similar problems. Diet, lifestyle and

environment affect our health, too. Ferrer's research also found that if teenagers feel they are ignored or

unimportant at home they are more likely to get sick.

     We may never fully understand all the effects that families have on our health. But just as individual

(个别的) problems can have effects on others, a small improvement can have big benefits, Ferrer said.

1. Which of the following can best explain why Wang Xiaoyu fainted in class?

A. Because her classmates often quarreled in class.

B. Because her parents used to quarrel.

C. Because of her depression caused by bad family relations.

D. Because her classmates shouted loudly at her.

2. According to Dr Ferrer, which of the following statements is TRUE?

A. We get sick or stay well by ourselves.

B. Only the genes we get from our family have a big effect on our health.

C. Our health has nothing to do with diet, lifestyle and environment.

D. Teenagers who are ignored at home get sick more easily than those who are not.

3. The underlined word "coma" in Paragraph2 probably means ________.

A. surprise    

B. faint        

C. tiredness

D. sadness

4. The best title for this passage is ________.

A. Family relations.                

B. The reasons why we get sick.

C. Family—another cause to health    

D. A research about health.

问答题 简答题