题干

(阅读下面材料,解答后面问题:

在数学课上,老师提出如下问题:

已知:Rt△ABC,∠ABC=90°

求作:矩形ABCD.

小敏的作法如下:

①作线段AC的垂直平分线交AC于点O;②连接BO并延长,在延长线上截取OD=BO;③连接DA,DC.则四边形ABCD即为所求.

判断小敏的作法是否正确?若正确,请证明;若不正确,请说明理由.

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答案(点此获取答案解析)

解:小敏的作法正确.理由如下:

∵线段AC的垂直平分线交AC于点O,

∴AO=CO,

∵BO=DO,

∴四边形ABCD为平行四边形,

∵∠ABC=90°,

∴四边形ABCD为矩形

同类题2

概要写作。阅读下面短文,根据其内容写一篇60词左右的内容概要。

    When a consumer finds that something he or she bought is faulty or in some other way does not live up to what the producer says for it, the first step is to present the warranty(保单),or any other records that might help, at the store of buying. In most cases, this action will produce results.

    However, if it does not, there are various means the consumer may use to gain satisfaction. A simple and common method used by many consumers is to complain directly to the store manager. In general, the “higher up” the consumer takes his or her complaint, the faster he or she can expect it to be settled. In such a case, it is usually settled in the consumer's favour, taking it as true that he or she has a just right.

    Consumers should complain in person whenever possible, but if they cannot get to the place of buying, it is acceptable to phone or write the complaint in a letter.

    Complaining is usually most effective when it is done politely but firmly, and especially when the consumer can show clearly what is wrong with what was bought in question. If this cannot be done, the consumer will succeed best by presenting specific information as to what is wrong, rather than by making general statements. For example, “The left speaker does not work at all and the sound coming out of the right one is unclear” is better than “This stereo(立体音响) does not work.”

    The store manager may advise the consumer to write to the producer, if so, the consumer should do this, stating the complaint as politely and as firmly as possible. But if a polite complaint does not achieve the expected result, the consumer can go a step further. He or she can threaten to take the seller to court or report the seller to a public organization responsible for protecting consumers' rights.