初二数学折叠问题 初二数学矩形折叠问题，求救！
\u521d\u4e2d\u6570\u5b66\u6298\u53e0\u95ee\u9898\uff0c\u9ad8\u624b\u8fdb\uff01\u5475\u5475 \u672c\u9898\u6dfb\u4e00\u6761\u8f85\u52a9\u7ebf\u5c31\u597d\u505a\u4e86
\u89e3\uff1a
\u8fc7\u70b9A\u4f5cAF\u5782\u76f4\u4e8eBC\u4ea4BC\u4e8eF
\u6613\u5f97\u5230\u25b3ACG\uff08G:AE,BC\u4ea4\u70b9\uff09\u662f\u7b49\u8170\u4e09\u89d2\u5f62
\u2234AG=CG
\u53c8\u2235G\u4e3aBC\u4e2d\u70b9\uff0cBC=8
\u2234BG=GC=AG=8/2=4
\u8bbeBF=x,\u5219FG=4-x
\u5728\u76f4\u89d2\u4e09\u89d2\u5f62ABF\u4e0e\u76f4\u89d2\u4e09\u89d2\u5f62AFG\u4e2d,AB=6,AG=4
\u5f97\u5230\u7b49\u5f0f
6^2-x^2=4^2-(4-x)^2
\u89e3\u5f97 x=4.5
\u2234BF=4.5
\u2234\u6613\u5f97AF=\u221a6^2-4.5^2=3\u221a7/2
\u2234\u9762\u79ef\u7b49\u4e8e12\u221a7
\u672c\u9898\u4e3b\u8981\u8003\u5bdf\uff081\uff09\u52fe\u80a1\u5b9a\u7406\uff082\uff09\u5e73\u884c\u56db\u8fb9\u5f62\u7684\u6027\u8d28\uff083\uff09\u7b49\u89d2\u5bf9\u7b49\u8fb9
(1)\u25b3BMP\u662f\u7b49\u8fb9\u4e09\u89d2\u5f62
\u8bc1\u660e\uff1a
\u8fde\u63a5AN
\u2235EF\u5782\u76f4\u5e73\u5206AB
\u2234AN\uff1dBN
\u7531\u6298\u53e0\u7684\u6027\u8d28\u53ef\u77e5\uff1a
AB\uff1dBN\uff0c\u2220ABM\uff1d\u2220MBN\uff0c\u2220BNM\uff1d\u2220A\uff1d90\u00b0
\u2234AN\uff1dAB\uff1dBN
\u2234\u25b3ABN\u662f\u7b49\u8fb9\u4e09\u89d2\u5f62
\u2234\u2220ABN\uff1d60\u00b0
\u2234\u2220ABM\uff1dMBN\uff1d1/2\u2220ABN\uff1d30\u00b0
\u2220NBP\uff1d\u2220ABC\uff0d\u2220ABN\uff1d30\u00b0
\u2234\u2220BPN\uff1d\u2220BNM\uff0d\u2220NBP\uff1d60\u00b0
\u2220MBP\uff1d\u2220MBN\uff0b\u2220NBP\uff1d60\u00b0
\u2234\u2220BMP\uff1d60\u00b0
\u2234\u2220BPN\uff1d\u2220MBP\uff1d\u2220BMP\uff1d60\u00b0
\u2234\u25b3BMP\u662f\u7b49\u8fb9\u4e09\u89d2\u5f62
(2)
\u8981\u5728\u77e9\u5f62\u7eb8\u7247ABCD\u4e0a\u526a\u51fa\u7b49\u8fb9\u25b3BMP\uff0c\u5219BC\u2265BP
\u5728Rt\u25b3BNP\u4e2d\uff0cBN\uff1dAB\uff1da\uff0c\u2220NBP\uff1d30\u00b0
\u2234cos\u2220NBP\uff1dBN/BP\uff1d\u221a3/2\uff0cBP\uff1dBN/(\u221a3/2)\uff1da/(\u221a3/2)
BC\u2265BP\uff0cb\u2265a/(\u221a3/2)
\u2234a\u2264\u221a3/2 b
\u2234\u5f53a\u2264\u221a3/2 b\u65f6\uff0c\u5728\u77e9\u5f62ABCD\u4e0a\u80fd\u526a\u51fa\u8fd9\u6837\u7684\u7b49\u8fb9\u25b3BMP
(3)
\u2235\u2220M'BC\uff1d60\u00b0
\u2234\u2220ABM'\uff1d90\u00b0\uff0d60\u00b0\uff1d30\u00b0
\u5728Rt\u25b3ABM'\u4e2d\uff0ctan\u2220ABM'\uff1dAM'/AB
\u2234tan30\u00b0\uff1dAM'/2
\u2234AM'\uff1d2\u00d7(\u221a3/3)\uff1d2\u221a3/3
\u2234M'\u7684\u5750\u6807\u4e3a(2\u221a3/3\uff0c2)
\u2235M'\u5728BM'(y\uff1dkx)\u4e0a
\u22342\uff1d2\u221a3/3k
\u89e3\u5f97k\uff1d\u221a3
\u5047\u8bbe\u25b3ABM' \u6cbfBM\u2032\u6298\u53e0\u540e\uff0c\u70b9A\u843d\u5728\u77e9\u5f62ABCD\u5185\u7684\u70b9\u4e3aA\u2032
\u8fc7A'\u4f5cA'H\u22a5BC\u4ea4BC\u4e8eH\uff0c
\u2235\u25b3A\u2018BM'\u224c\u25b3ABM\u2019
\u2234\u2220A'BM'\uff1d\u2220ABM'\uff1d30\u00b0\uff0cA'B\uff1dAB\uff1d2
\u2234\u2220A'BH\uff1dM'BC\uff0d\u2220A'BM'\uff1d30\u00b0
\u5728Rt\u25b3A'BH\u4e2d\uff0c\u2220A'BH\uff1d30\u00b0
\u2234A'H\uff1d1/2A'B\uff1d1(30\u00b0\u6240\u5bf9\u7684\u76f4\u89d2\u8fb9\u7b49\u4e8e\u659c\u8fb9\u7684\u4e00\u534a)\uff0cBH\uff1d\u221a3
\u2234A'\u7684\u5750\u6807\u4e3a(\u221a3\uff0c1)
\u2234\u70b9A\u843d\u5728EF\u4e0a
因为CD=5,CB'=2,得出A'B'=1 OA'=OB'=0.5(俩三角形全等)。
因为CB'=2,三角形CAB'为345三角形，得B'F=2.25。
因为BF'=2.25，OB'=0.5，得OF=四分之根号十，既EF等于二分之根号十。
这是正方形吗？BC=4，BD=3
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绛旓細绛旀鍙兘鏄垹BDA+鈭燙EA=2鈭燗 鍥涜竟褰负360搴 鍦ㄥ洓杈瑰舰bcde涓垹B+鈭燙+鈭燘DE+鈭燚EC=360掳 锛1锛夊湪涓夎褰BC涓垹b+鈭燾=180掳-鈭燼 锛2锛夊湪涓夎褰de涓垹ade+鈭燼ed=180掳-鈭燼 锛3锛夆垹bde=鈭燽da+鈭燼de (4)鈭燿ec=鈭燼ec+鈭燼ed ...
绛旓細濡傚浘锛屾部EF鎶樺彔锛孉C閲嶅悎,姝ゆ椂AE=EC 璁 BE涓簒,AE^2=AB^2+BE^2 鎵浠 锛4-x)^2=3^2+x^2 鎵浠=7/8 鎵浠 閲嶅彔閮ㄥ垎涓夎褰EF鐨勯潰绉负 锛3*4)/2 -(3*7/8)/2=75/16
绛旓細鐩存帴2闂紙灏忓啓浜嗭級ae=1 鏄撳緱be=2 鐒惰宔d=be=2 鎵浠d=3 鏍规嵁鍕捐偂锛堜篃鍙互涓夎鍑芥暟锛夊緱 ab=鏍瑰彿3 鎵浠=ab*bc =鏍瑰彿3 * 3=3*鏍瑰彿3
绛旓細瑙ｏ細璁綝F=x锛孋F=16-x銆傜敱棰樺彲寰桝B=EB锛屸垹A=鈭燛銆傚湪鐭╁舰ABCD涓紝鈭燗=鈭燙=90掳锛孉B=CD=12銆傚張鈭礎B=EB锛屸垹A=鈭燛銆傗埓EB=CD锛屸垹E=鈭燙銆傚湪鈻矪FE鍜屸柍DFC涓紝鈭燛=鈭燙锛屸垹BFE=鈭燚FC锛孍B=CD銆傗埓鈻矪FE鈮屸柍DFC锛圓AS锛夈傗埓BF=DF=x銆傚湪RT鈻矰CF涓紝鈭燙=90掳銆傗埓DC²+CF²=...
绛旓細棣栧厛涓夎褰EF鏄洿瑙掍笁瑙掑舰锛屼笖DF=DA=6锛岃AE=EF=x锛屽埄鐢ㄧ洿瑙掍笁瑙掔嚎BEF鍕捐偂瀹氱悊锛屾湁X鐨勫钩鏂+锛10-6锛夌殑骞虫柟=锛8-x锛夌殑骞虫柟锛岃В寰梮绛変簬2.5锛屾墍浠ラ潰绉瓑浜7.5
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