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【简答题】
(1)问题探究 数学课上,老师给出以下命题,要求加以证明. 如图1,在△ABC中,M为BC的中点,且MA= BC,求证∠BAC=90°. 同学们经过思考、讨论、交流,得到以下证明思路: 思路一 直接利用等腰三角形性质和三角形内角和定理… 思路二 延长AM到D使DM=MA,连接DB,DC,利用矩形的知识… 思路三 以BC为直径作圆,利用圆的知识… 思路四… 请选择一种方法写出完整的证明过程; (2)结论应用 老师要求同学们很好地理解(1)中命题的条件和结论,并直接运用(1)命题的结论完成以下两道题: ①如图2,线段AB经过圆心O,交⊙O于点A,C,点D在⊙O上,且∠DAB=30°,OA=a,OB=2a,求证:直线BD是⊙O的切线; ②如图3,△ABC中,M为BC的中点,BD⊥AC于D,E在AB边上,且EM=DM,连接DE,CE,如果∠A=60°,请求出△ADE与△ABC面积的比值.
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A.
which is the Mark 2 project.
B.
when we look at this question.
C.
that values his new ideas.
D.
that the process can be made simpler.
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A.
use of color
B.
use of light
C.
use of space
D.
use of text
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A.
What questions should be asked at the beginning because they are easy to answer and answering them will assure the interviewee that your questions are manageable?
B.
What questions should be asked at the beginning because they are foundational to what you will ask later or because they will give you time to promote rapport?
C.
What questions should be asked in special order?
D.
What questions should be kept as far apart as possible because you want to minimize the influence of one question on the answer to another?
E.
What questions should be asked at the end because of their nature as summaries?
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age
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gender
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economic level
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language
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A.
50%~59%
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40%~50%
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30%~40%
D.
30%以下
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A.
社会保险费
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其他长期职工福利
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职工福利费
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辞退福利
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正确
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错误
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3′ , 5′- 磷酸二酯键
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2′ , 3′- 磷酸二酯键
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2′ , 5′- 磷酸二酯键
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A.
nose
B.
goat
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hen
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poem
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