2017关于八年级数学上册期末试卷及答案（人教版）
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一、细心填一填(本大题共有10小题，16空，每空2分，共32分.请把结果直接填在题中的横线上.只要你
理解概念，仔细运算，积极思考，相信你一定会填对的!) 1.16的平方根是________;25的算术平方根是________;若y3=-8，则y=________. 2.计算：(1)a÷a=________;(2)(m+2n)(m-2n)=__________;
(3)(4a3b2-6a2b2+2ab)÷2ab=_________________.
3.如图，△ABC中，∠ABC=36，BC=6cm，E为BC的中点，平移
△DEF，则∠DEF=________，平移距离为_________cm. 4.我们知道，所有的正多边形都是旋转对称图形.其中，正九边形绕
心至少旋转________后才能与原图形重合.
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4
AB
……此处隐藏2044个字……/p>
在等边△ABC中，作AF⊥BC于F，则BF=CF=2，„„„„„„„„„„„„„„„(6分) ∴在Rt△ABF中，AF2–BF2 ， „„„„„„„„„„„„„„„„„„(7分)
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∴S阴影=S△ABC=×4×2=4„„„„„„„„„„„„„„„„„„„„„„(8分)
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四、动脑想一想(本题满分10分.) 24.
(1
图① 图③
连结DN，则∵ON⊥BD，O是BD的中点，∴ON垂直平分BD，„„„„„„„„„(1分)
∴DN=BN，„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„„(2分) 在Rt△DCN中，DN2=CD2+CN2，„„„„„„„„„„„„„„„„„„„„„„(3分) ∴BN2=CD2+CN2 (2)BN、CN、CM、DM这四条线段之间的关系为BN2+DM2=CN2+CM2.„„„„„(5分)
延长NO交AD于点P，连结MN、MP.由“O为矩形ABCD的对角线交点”，通过全等或旋转对称可说明BN=DP，OP=ON，„(6分)∴OM垂直平分PN，∴MP=MN.„„(7分)
在Rt△MDP中，MP2=DP2+DM2，„„„„„„„„„„„„„„„„„„„„„„(8分) 在Rt△MCN中，MN=CN+CM，„„„„„„„„„„„„„„„„„„„„„„(9分) 又∵MP=MN，BN=DP，∴BN2+DM2=CN2+CM2.„„„„„„„„„„„„„„(10分)
