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. ． (——青夏教育精英家教网—

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)

（2011山东烟台，26，14分）

如图，在直角坐标系中，梯形ABCD的底边AB在x轴上，底边CD的端点D在y轴上.直线CB的表达式为y=－x+，点A、D的坐标分别为（－4，0），（0，4）.动点P自A点出发，在AB上匀速运行.动点Q自点B出发，在折线BCD上匀速运行，速度均为每秒1个单位.当其中一个动点到达终点时，它们同时停止运动.设点P运动t（秒）时，△OPQ的面积为s（不能构成△OPQ的动点除外）.

（1）求出点B、C的坐标；

（2）求s随t变化的函数关系式；

（3）当t为何值时s有最大值？并求出最大值.

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（2011山东烟台，26，14分）
如图，在直角坐标系中，梯形ABCD的底边AB在x轴上，底边CD的端点D在y轴上.直线CB的表达式为y=－

，点A、D的坐标分别为（－4，0），（0，4）.动点P自A点出发，在AB上匀速运行.动点Q自点B出发，在折线BCD上匀速运行，速度均为每秒1个单位.当其中一个动点到达终点时，它们同时停止运动.设点P运动t（秒）时，△OPQ的面积为s（不能构成△OPQ的动点除外）.
（1）求出点B、C的坐标；
（2）求s随t变化的函数关系式；
（3）当t为何值时s有最大值？并求出最大值.

查看答案和解析>>

（2011山东烟台，26，14分）
如图，在直角坐标系中，梯形ABCD的底边AB在x轴上，底边CD的端点D在y轴上.直线CB的表达式为y=－x+，点A、D的坐标分别为（－4，0），（0，4）.动点P自A点出发，在AB上匀速运行.动点Q自点B出发，在折线BCD上匀速运行，速度均为每秒1个单位.当其中一个动点到达终点时，它们同时停止运动.设点P运动t（秒）时，△OPQ的面积为s（不能构成△OPQ的动点除外）.
（1）求出点B、C的坐标；
（2）求s随t变化的函数关系式；
（3）当t为何值时s有最大值？并求出最大值.