发布时间 : 星期一 文章2012湖北省咸宁市数学中考试题 2更新完毕开始阅读3ef1983a10661ed9ad51f3e9
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而FC?FC，
∴Rt△FCE≌Rt△FCM． ∴EF?MF，EC?MC．
······························· 6分
同理：NH?EH，NB?EB．
∴MN?2BC?16． ······························································································ 7分 ∵?M?90???5?90???1，?N?90???3， ∴?M??N． ∴GM?GN． ····································································· 8分 过点G作GK⊥BC于K，则KM?1················································· 9分 MN?8． ·
2∴GM?GK2?KM2?42?82?45．
∴四边形EFGH的周长为2GM?85． ··························································· 10分 证法二：∵?1??2，?1??5， ∴?2??5． 而FC?FC， ∴Rt△FCE≌Rt△FCM． ∴EF?MF，EC?MC． ··················································································· 6分 ∵?M?90???5?90???1，?HEB?90???4，
而?1??4， ∴?M??HEB． ∴HE∥GF． 同理：GH∥EF． ∴四边形EFGH是平行四边形． ·········································································· 7分 ∴FG?HE． 而?1??4， ∴Rt△FDG≌Rt△HBE． ∴DG?BE． ····················································· 8分 过点G作GK⊥BC于K，则KM?KC?CM?GD?CM?BE?EC?8． ······ 9分 ∴GM?GK2?KM2?42?82?45． ∴四边形EFGH的周长为2GM?85． ··························································· 10分 24．解：（1）∵?CAO??BAE?90?，?ABE??BAE?90?， ∴?CAO??ABE． ∴Rt△CAO∽Rt△ABE． ······················································································· 2分
CAAO． ?ABBE2ABt∴························································································ 3分 ?．∴t?8． ·AB41（2）由Rt△CAO∽Rt△ABE可知：BE?t，AE?2． ································· 4分
211t25当0＜t＜8时，S?CD?BD?(2?t)(4?)?．
2224∴
∴t1?t2?3． ········································································································· 6分 当t＞8时，S?CD?BD?121t25． (2?t)(?4)?224∴t1?3?52，t2?3?52（为负数，舍去）． 当t?3或3?52时，S?25． ··········································································· 8分 421世纪教育网 -- 中国最大型、最专业的中小学教育资源门户网站。 版权所有@21世纪教育网
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（3）过M作MN⊥x轴于N，则MN?CO?2．
y C x=5 D B 12当MB∥OA时，BE?MN?2，OA?2BE?4． ········· 9分 抛物线y?ax2?10ax的顶点坐标为（5，?25a）． ·· 10分 它的顶点在直线x?5上移动．
直线x?5交MB于点（5，2），交AB于点（5，1）．11分 ∴1＜?25a＜2． ∴? O A （第24题） E x 21＜a＜?． ··················································· 12分 2525
试题平稳 稳中求新
点评人：温中数学老师 石 娟
总体来说，今年中考数学试卷试题整体坡度平缓，依标靠本，基础性强，大部分题目都立足于考查初中数学的核心基础知识、基本技能及隐含于其中的基本数学思想方法，同时注意结合现实背景，体现对数学本质理解的考查。
与去年相比，题型、题量、题目的赋分比较平稳，题型没有变化，填空题、选择题各有一道创新题，呈现出稳中求新的特点。其中，选择题第8题和填空题14题是本套试题最大的亮点，有新意。第8题以学生非常喜欢的一档电视娱乐节目为题干，考查学生视图的基本能力。 14题考查圆的相关知识，包含的知识点丰富，有圆周角、圆心角等，考生需要认真读懂题意，理清头绪，才能准确作答。试题入手容易，细做难，且难度有所分解，“三基”考查到位，基本的活动经验有体现，对优等生来说，做起来顺手，中等生要将试题完整地解答出来，有一定的难度。
此外，试卷的信度和区分度较高，试题的综合能力强，考查学生的数学解读能力，知识掌握能力和知识迁移能力，需要学生将课内知识与课外知识有效结合，发现规律后懂得拓展运用。
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