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九年级数学解答题一般
题目
如图,菱形ABCDABCD的对角线ACACBDBD相交于点O,BEO,BEAC,AEAC,AEBDBD,OEOEABAB交于点FF.
(1)(1)求证:四边形AEBOAEBO的为矩形;
(2)(2)OE=10OE=10,AC=16AC=16,求菱形ABCDABCD的面积.
知识点:矩形的判定、菱形的性质章节:第1章 特殊的平行四边形 / 1.2 矩形的性质与判定

答案与解析

答案

(1)(1)证明:BE\because BEAC,AEAC,AEBDBD
\therefore四边形AEBOAEBO是平行四边形,
\because菱形ABCDABCD对角线交于点OO
ACBD\therefore AC\bot BD
AOB=90\therefore \angle AOB=90^{\circ}
\therefore四边形AEBOAEBO为矩形;
(2)(2)\because四边形ABCDABCD是菱形,AC=16AC=16
OA=12AC=8\therefore OA=\frac{1}{2}AC=8OB=ODOB=ODACBDAC\bot BD
\because四边形AEBOAEBO是矩形,
AB=OE=10\therefore AB=OE=10
OB=AB2OA2=10282=6\therefore OB=\sqrt{A{B}^{2}-O{A}^{2}}=\sqrt{1{0}^{2}-{8}^{2}}=6
BD=2OB=12\therefore BD=2OB=12
\therefore菱形ABCDABCD的面积=12ACBD=12×16×12=96=\frac{1}{2}AC\cdot BD=\frac{1}{2}\times 16\times 12=96.

解析

(1)(1)证明:BE\because BEAC,AEAC,AEBDBD
\therefore四边形AEBOAEBO是平行四边形,
\because菱形ABCDABCD对角线交于点OO
ACBD\therefore AC\bot BD
AOB=90\therefore \angle AOB=90^{\circ}
\therefore四边形AEBOAEBO为矩形;
(2)(2)\because四边形ABCDABCD是菱形,AC=16AC=16
OA=12AC=8\therefore OA=\frac{1}{2}AC=8OB=ODOB=ODACBDAC\bot BD
\because四边形AEBOAEBO是矩形,
AB=OE=10\therefore AB=OE=10
OB=AB2OA2=10282=6\therefore OB=\sqrt{A{B}^{2}-O{A}^{2}}=\sqrt{1{0}^{2}-{8}^{2}}=6
BD=2OB=12\therefore BD=2OB=12
\therefore菱形ABCDABCD的面积=12ACBD=12×16×12=96=\frac{1}{2}AC\cdot BD=\frac{1}{2}\times 16\times 12=96.

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