题干

如图所示,某教学活动小组选定测量山顶铁塔AE的高,他们在30m高的楼CD的底部点D测得塔顶A的仰角为45°,在楼顶C测得塔顶A的仰角为36°52′.若小山高BE=62m,楼的底部D与山脚在同一水平面上,求铁塔的高AE.(参考数据:sin36°52′≈0.60,tan36°52′≈0.75)

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答案(点此获取答案解析)

解:如图,过点C作CF⊥AB于点F.

设塔高AE=x,作CF⊥AB于点F,

则四边形BDCF是矩形,

∴CD=BF=30m,CF=BD,

∵在Rt△ADB中,∠ADB=45°,

∴AB=BD=x+62

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    People who smoke could lose around one third of their everyday memory, researchers say.

    A study by a team at the University of Northumbria has shown that smokers lose more of their memory when compared to non-smokers. And the research also found that those who kicked the habit saw their ability to recollect information restored to almost the same level as non-smokers.

    The study involved more than seventy 18-to 25-year-old volunteers and included a tour of the university's campus. Those who took part were asked to recall(回忆;回想)small details, such as music acts listed to play at the students' union and tasks completed at various points---known as a real-world memory test.

    Smokers performed badly, remembering just 59 percent of tasks. But those who had given up smoking remembered 74 percent and those who had never smoked recalled 81 percent of tasks.

    Dr. Tom Heffernan, who leads Northumbria University's Collaboration for Drug and Alcohol Research Group, said the findings would be useful in anti-smoking campaigns. He said, “Given that there are up to 10 million smokers in the UK and as many as 45 million in America, it's important to understand the effects that smoking has on everyday cognitive function.”

    This is the first time that a study has set out to examine whether giving up smoking has an effect on memory. We already know that giving up smoking has huge health benefits to the body, but this study also shows how stopping smoking can bring a series of benefits to cognitive function. The research will now investigate the effects of second-hand smoking on memory, while Dr. Heffernan will look into third-hand smoking, such as toxins (毒素) left on curtains and furniture.