题干

如图,小强在河的一边,要测河面的一只船B与对岸码头A的距离,他的做法如下:

①在岸边确定一点C,使C与A,B在同一直线上;

②在AC的垂直方向画线段CD,取其中点O;

③画DF⊥CD使F、O、A在同一直线上;

④在线段DF上找一点E,使E与O、B共线.

他说测出线段EF的长就是船B与码头A的距离.他这样做有道理吗?为什么?

上一题 下一题 0.0难度 选择题 更新时间:2017-03-03 12:51:50

答案(点此获取答案解析)

解:有道理,∵DF⊥CD,AC⊥CD,∴∠C=∠D=90°,∵O为CD中点,∴CO=DO,在△ACO和△FDO中 {C=DCO

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    Health experts are calling for action to increase cancer care and control in the developing world. A medical research paper says cancer was once thought of as a problem mostly in the developed world. But now cancer is a leading cause of death and disability in poor countries as well. Experts from Harvard University and other organizations urge the international community to fight cancer actively, saying it should be fought in the way HIV/AIDS has been fought in Africa.

    Cancer kills more than 7.5 million people a year worldwide. Almost two thirds are in low-income and middle-income countries.

    They discover cancer kills more people in developing countries than AIDS, tuberculosis and malaria combined. But the world spends only 5﹪ of its cancer resources in those countries.

    Felicia Knaul from Harvard Medical School was one of the writers of the paper. She was in Mexico when she was found to have breast cancer. She received treatment there and her experience showed her the sharp difference between the rich and the poor in treating breast cancer.

    Felicia Knaul says, “And we are seeing how this is attacking young women. It's the number two cause of death in Mexico of women thirty to fifty-four. All over the developing world, it's the number one cancer-related death among young women. I think we have to again say that there is much more we could do about it than we are doing about it. ”

    Professor Knaul met community health workers during her work in developing countries. They were an important part of efforts to reduce deaths from the cancer. They were able to persuade people to get tested to prevent the illness. The experts say cancer care does not have to be costly. For example, patients can be treated with lower-cost drugs.