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    26． (1)如图1.图2.图3.在中.分别以为边.向外作正三角形.正四边形.正五边形.相交于点． ①如图1.求证:, ②探究:如图1. , 如图2. , 如图3. ． (2)如图4.已知:是以为边向外所作正边形的一组邻边,是以为边向外所作正边形的一组邻边．的延长相交于点． ①猜想:如图4. (用含的式子表示), ②根据图4证明你的猜想． (1)①证法一:与均为等边三角形. .························································································ 2分 且··············································· 3分 . 即························································ 4分 ．··················································· 5分 证法二:与均为等边三角形. .························································································ 2分 且························································································ 3分 可由绕着点按顺时针方向旋转得到··································· 4分 ．··························································································· 5分 ②..．········································································ 8分 (2)①········································································································ 10分 ②证法一:依题意.知和都是正边形的内角... .即．····························· 11分 ．·························································································· 12分 ..······ 13分 . ········································ 14分 证法二:同上可证 ．··························································· 12分 .如图.延长交于. . ································ 13分 ················· 14分 证法三:同上可证 ．··························································· 12分 ． . ························································ 13分 即········································································ 14分 证法四:同上可证 ．··························································· 12分 ．如图.连接. ．···································· 13分 即······························· 14分 注意:此题还有其它证法.可相应评分． 【查看更多】

     

    题目列表(包括答案和解析)

    如图（1）是夹文件用的铁（塑料）夹子在常态下的侧面示意图．AC，BC表示铁夹的两个面，O点是轴，OD⊥AC于D．已知AD=15mm，DC=24mm，精英家教网OD=10mm．已知文件夹是轴对称图形，试利用图（2），求图（1）中A，B两点的距离（：
    		676
    =26）．

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    下列定义一种关于正整数n的“F运算”：①当n是奇数时，F=3n+5；②n为偶数时，结果是F=n×
    1
    2
    ×
    1
    2
    ×
    1
    2
    ×…    （其中F是奇数），并且运算重复进行．例如：取n=26，如图，若n=50，则第2012次“F运算”的结果是（　　）

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    如图给出的是某日历表，
    一 二 三 四 五 六 日
    1 2 3
    4 5 6 7 8 9 10
    11 12 13 14 15 16 17
    18 19 20 21 22 23 24
    25 26 27 28 29 30 31
    （1）在日历表中任意圈出三个数，如果设第一行第一个数为x，请你运用方程的思想列式来表示图1、图2中这三个数的和．
    （2）如果这三个数的和是35，那么这个数阵的形式可能是图
    2
    2
    ．
    （3）图1中三个数之和能等于47吗？若能，请写出这三个数；若不能，说明理由．

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    2、如图，14，26分别为所在正方形的面积，则图中字母A所代表的正方形的面积A=
    12
    ．

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    如图（1）是夹文件用的铁（塑料）夹子在常态下的侧面示意图．AC，BC表示铁夹的两个面，O点是轴，OD⊥AC于D．已知AD=15mm，DC=24mm，OD=10mm．已知文件夹是轴对称图形，试利用图（2），求图（1）中A，B两点的距离（：=26）．

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