问题 选择题

已知三角形的两边长分别为3cm和8cm,则这个三角形的第三边的长可能是

A.4cm

B.5cm

C.6cm

D.13cm

答案

答案:C

已知三角形的两边长分别为3cm和8cm,根据在三角形中任意两边之和>第三边,任意两边之差<第三边;即可求第三边长的范围.

解:设第三边长为x,则由三角形三边关系定理得8-3<x<8+3,即5<x<11.

因此,本题的第三边应满足5<x<11,把各项代入不等式符合的即为答案.

4,5,13都不符合不等式5<x<11,只有6符合不等式,故答案为6cm.故选C.

点评:此类求三角形第三边的范围的题,实际上就是根据三角形三边关系定理列出不等式,然后解不等式即可

阅读理解

阅读理解。

     Do you want to live a happier, less stressful (有压力的) life? Try laughing for no reason at all. That's

how thousands of people start their day at Laughter Clubs around the world-and many doctors now think

that having a good laugh might be one of the best ways to stay healthy.

     The first Laughter Club was started in Mumbai, India, in 1995 by Dr Madan Kataria. "Young children

laugh about 300 times a day. Adults laugh between 7and 15 times a day," says Dr Kataria. "Everyone's

naturally good at laughing-it' s the universal language. We want people to feel happy with their lives." There

are now more than 500 Laughter Clubs in India and over 1, 300 worldwide.

      Many doctors are also interested in the effects (效果) of laughter on our health. According to a 5-year

study at the UCLA School of Medicine in California, with laughing there is less stress in the body. Laughter

improves our health against illness by about 40%.

     So, what happens at a Laughter Club? I went along to my nearest club in South London to find out. I was

quite nervous at the beginning of the class, to be honest-I wasn't interested in laughing with a group of strangers, and I was worried about looking stupid. Our laughter teacher told us to clap our hands and say"ho ho ho, ha

ha ha," while looking at each other. However, our bodies can' t tell the difference between fake laughter and

real laughter, so they still produce the same healthy effects.

     Surprisingly, it works! After ten minutes everybody in the room was laughing for real and some people

just couldn't stop! At the end of the class I was surprised by how relaxed and comfortable I felt. So if you're

under stress, then start laughing. You might be very pleased with the results!

1. In which country was the first Laughter Club started?

A. Britain.

B. America.

C. Australia.

D. India.

2. How did the writer feel at the beginning of the class?

A. Surprised.

B. Pleased.

C. Nervous.

D. Stressful.

3. When did the people in the club begin to laugh for real?

A. After a few minutes.

B. After a few hours.

C. After a few seconds.

D. After a few days.

4. Which of the following is true according to the passage?

A. Fake laughter and real laughter are both good for health.

B. 40% of the people in Laughter Clubs are good friends.

C. Adults laugh more often than children in a day.

D. Laughing is the best way to prevent illness.

问答题 简答题