23．（本小题满分7分）
某数学兴趣小组，利用树影测量树高，如图（1），已测出树AB的影长AC为12米，并测出此时太阳光线与地面成30°夹角．(2≈1.4，3≈1.7)
（1）求出树高AB；
（2）因水土流失，此时树AB沿太阳光线方向倒下，在倾倒过程中，树影长度发生了变化，假设太阳光线与地面夹角保持不变．（用图（2）解答） ①求树与地面成45°角时的影长； ②求树的最大影长．
第23题图
24．（本小题满分9分）
如图，AB为⊙O的直径，劣弧BC?BE，BD∥CE，连接AE并延长交BD于D． 求证：（1）BD是⊙O的切线；
·AD． （2）AB?AC
2第24题图
25．（本小题满分10分）
在实施“中小学校舍安全工程”之际，某市计划对A、B两类学校的校舍进行改造，根据预算，改造一所A类学校和三所B类学校的校舍共需资金480万元，改造三所A类学校和一所B类学校的校舍共需资金400万元．
（1）改造一所A类学校的校舍和一所B类学校的校舍所需资金分别是多少万元？
（2）该市某县A、B两类学校共有8所需要改造．改造资金由国家财政和地方财政共同承担，若国家财政拨付的改造资金不超过770万元，地方财政投入的资金不少于210万元，其中地方财政投入到A、B两类学校的改造资金分别为每所20万元和30万元，请你通过计算求出有几种改造方案，每个方案中A、B两类学校各有几所．
26．（本小题满分11分）
如图，四边形OABC是一张放在平面直角坐标系的矩形纸片，O为原点，点A在x轴上，点C在y轴上，OA?15，OC?9，在AB上取一点M，使得△CBM沿CM翻折后，点B落在x轴上，记作N点．
（1）求N点、M点的坐标；
（2）将抛物线y?x2?36向右平移a(0?a?10)个单位后，得到抛物线l，l经过N点，求抛物线l的解析式；
（3）①抛物线l的对称轴上存在点P，使得P点到M，N两点的距离之差最大，求P点的坐标；②若点D是线段OC上的一个动点（不与O、C重合），过点D作DE∥OA交CN于E，设CD的长为m，△PDE的面积为S，求S与m之间的函数关系式，并说明S是否存在最大值．若存在，请求出最大值；若不存在，请说明理由．
第26题图
20XX年鄂尔多斯市初中毕业升学考试
数学试题参考答案及评分说明
（一）阅卷评分说明
1．正式阅卷前先进行试评，在试评中认真阅读参考答案，明确评分标准，不得随意拔高或降低评分标准．试评的试卷必须在阅卷后期予以复查，防止前后期评分标准宽严不一致．
2．评分方式为分步累计评分，解答过程的某一步骤发生笔误，只要不降低后继部分的难度，而后继部分再无新的错误，后继部分可评应得分数的50%；若是几个相对独立的得分点，其中一处错误不影响其它得分点的评分．
3．最小记分单位为1分，不得将评分标准细化至1分以下（即不得记小数分）．
4．解答题题头一律记该题的实际得分，不得用记负分的方式记分．对解题中的错误须用红笔标出，并继续评分，直至将解题过程评阅完毕，并在最后得分点处标上该题实际得分．
5．本参考答案只给出一至两种解法，凡有其它正确解法都应参照本评分说明分步确定得分点，并同样实行分步累计评分．
6．合理精简解题步骤者，其简化的解题过程不影响评分． （二）参考答案及评分标准
一、选择题（本大题10个小题，每小题3分，共30分）
1 2 3 4 5 6 7 8 9 10 题 号 选项 C B D D B D A C 15．4n?1
B D 二、填空题（本大题8个小题，每小题3分，共24分）
11．x≥2 12．a?5 13.28 14.8，8.2 16．m??6且m??4
17．18(18°)
18．3
三、解答题（本大题8个小题，共66分） 19．（本小题满分8分）
?1?（1）计算：?2?3?27????(π?2)0
?3?2?1解：原式=?4?3?3 ················································································· 3分（一处正确给1分） ??10． ········································································································································· 4分
a2?b2?2ab?b2?（2）先化简：再求值：2??a??，其中a?2?1，b?1．
a?ab?a?(a?b)(a?b)(a?b)2解：原式= ························································ 2分（一处正确给1分） ?a(a?b)a=
1 ············································································································································· 3分 a?b?12 ························································································································ 4分 ?2?1?12 20．（本小题满分7分）
景点 成陵 响沙湾 恩格贝 七星湖 巴图湾
解：（1）84?21%?400（人）．答：共调查了400人． ······················································ 2分 400?25%?100（人），补充图表如下 ································································· 4分（各1分） （2）360°?21%?75.6°．答：“恩格贝”所对的圆心角是75.6°． ··································· 6分 （3）2500?29%?725（人）．答：首选去成陵的人数约725人． ···································· 7分 21．（本小题满分6分） 解：（1）树状图：
···························································· 3分
P(组成三角形)?42·············································································································· 5分 ?． ·
63频数 116 100 84 63 37 频率 29% 25% 21% 15.75% 9.25% 1（2）P(组成直角三角形)?． ···································································································· 6分
622．（本小题满分8分） （1）证法一： 如图（1），延长AD交FE的延长线于N，
?NDE??FCE?90°，图（1） ?△NDE≌△FCE． ················································································································· 3分 ?DN?CF． ······························································································································· 4分 AB∥FN，AN∥BF，?四边形ABFN是平行四边形． ··············································· 5分 ?BF?AD?DN?AD?FC． ······························································································· 6分
??1??BEF.?1??2，??2??BEF． （2）解：AB∥EF，?EF?BF．································································································································ 7分
?DEN??FEC，DE?EC，
相关推荐：
loading