2012年中考数学模拟试题(3)

2019-01-26 19:40

数学试卷

GB?BD?cos30°?100?3·········································································· 6分 ?503. ·

2在Rt△ADG中,?GDA?105°?60°?45? ··································································· 7分 ∴GD?GA?50, ·············································································································· 8分 ∴AB?AG?GB?50?503(米) ··············································································· 9分 答:索道长50?503米. ········································································································ ·············································································································································· 10分 25. (1)描点略. ·············································································································· 1分 设y?kx?b,用任两点代入求得y??100x?5000, ·················································· 3分 再用另两点代入解析式验证. ···························································································· 4分 (2)?y?z,??100x?5000?400x,

···························································································································· 6分 ?x?10. ·

······································································· 7分 ?总销售收入?10?4000?40000(元) ·

?农副产品的市场价格是10元/千克,

农民的总销售收入是40000元. ························································································ 8分 (3)设这时该农副产品的市场价格为a元/千克,

则a(?100a?5000)?40000?17600, ·········································································· 10分 解之得:a1?18,a2?32.

································································································ 11分 ?0?a?30,?a?18. ·

······························································ 12分 ?这时该农副产品的市场价格为18元/千克. ·

?, AC?CD26. (1)证明:∵C是?AD的中点,∴?∴∠CAD=∠ABC???????????????????1分 ∵AB是⊙O的直径,∴∠ACB=90°。 ∴∠CAD+∠AQC=90°

又CE⊥AB,∴∠ABC+∠PCQ=90°

∴∠AQC=∠PCQ???????????????????2分 ∴在△PCQ中,PC=PQ,

AC??AE ∵CE⊥直径AB,∴?? AE?CD∴?∴∠CAD=∠ACE。

∴在△APC中,有PA=PC,???????????????????3分 ∴PA=PC=PQ

∴P是△ACQ的外心。???????????????????4分

第 11页(全卷共8页)

数学试卷

(2)解:∵CE⊥直径AB于F, ∴在Rt△BCF中,由tan∠ABC=得BF?CF3?,CF=8, BF4432CF?。???????????????????5分 3340???????????????????6分 3∴由勾股定理,得BC?CF2?BF2?∵AB是⊙O的直径,

∴在Rt△ACB中,由tan∠ABC=

得AC?AC340 ?,BC?BC433BC?10。???????????????????7分 4易知Rt△ACB∽Rt△QCA,∴AC2?CQ?BC

AC215∴CQ??。???????????????????8分

BC2(3)证明:∵AB是⊙O的直径,∴∠ACB=90°

∴∠DAB+∠ABD=90°

又CF⊥AB,∴∠ABG+∠G=90° ∴∠DAB=∠G;

∴Rt△AFP∽Rt△GFB,???????????????????10分 ∴

AFFP,即AF?BF?FP?FG ?FGBF易知Rt△ACF∽Rt△CBF,

∴FG2?AF?BF(或由射影定理得)

∴FC2?PF?FG???????????????????11分 由(1),知PC=PQ,∴FP+PQ=FP+PC=FC

∴(FP?PQ)2?FP?FG。???????????????????12分

27(1)C(3,2),D(1,3);???????????????????2分

(2)设抛物线为y?ax2?bx?c,抛物线过(0,1),(3,2),(1,3),

第 12页(全卷共8页)

数学试卷

5?a??,?6?c?1,?17??,???????????????????4分 ?a?b?c?3,解得?b?6?9a?3b?c?2.???c?1.??∴y??5217x?x?1.???????????????????????5分 66(3)①当点A运动到点F时,t?1,

当0?t?1时,如图1,

∵?OFA??GFB', tan?OFA?∴tan?GFB'?∴S?FB'G?OA1?, OF2GB'GB'15??,∴GB'?t,

2FB'25t图1

115t52FB'?GB'??5t??t;??8分 2224 ②当点C运动到x轴上时,t?2,

当1?t?2时,如图2,

A'B'?AB?22?12?5,

∴A'F?5t?5,∴A'G?图2

5t?5, 2∵B'H?5t, 2∴S梯形A'B'HG?(A'G?B'H)?A'B' ?1215t?55t(?)?5 222?

图3

55t?;????(10分) 24③当点D运动到x轴上时,t?3, 当2?t?3时,如图3,

第 13页(全卷共8页)

数学试卷

∵A'G?5t?5, 25t?535?5t, ?22∴GD'?5?∵S?AOF?1?1?2?1,OA?1, 2图4

?AOF∽?GD'H SGD'2), ∴?GD'H?(S?AOFOA∴S?GD'H?(35?5t2), 235?5t2) 22∴S五边形GA'B'C'H?(5)?( =?521525t?t?.???(12分) 424(解法不同的按踩分点给分)

∵t?3,BB'?AA'?35,

∴S阴影?S矩形BB'C'C?S矩形AA'D'D ??????????????????(13分) =AD?AA'

=5?35?15.???????????????????????(14分)

第 14页(全卷共8页)


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