如图,在三角形ABC中,∠C=2∠A,AC=2CB,求证∠B=90°图片链接:file://C:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files\Content.IE5\ECSFNTNT\1112254132_828193240[1].jpg
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![如图,在三角形ABC中,∠C=2∠A,AC=2CB,求证∠B=90°图片链接:file://C:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files\Content.IE5\ECSFNTNT\1112254132_828193240[1].jpg](/uploads/image/z/3030114-66-4.jpg?t=%E5%A6%82%E5%9B%BE%2C%E5%9C%A8%E4%B8%89%E8%A7%92%E5%BD%A2ABC%E4%B8%AD%2C%E2%88%A0C%3D2%E2%88%A0A%2CAC%3D2CB%2C%E6%B1%82%E8%AF%81%E2%88%A0B%3D90%C2%B0%E5%9B%BE%E7%89%87%E9%93%BE%E6%8E%A5%EF%BC%9Afile%3A%2F%2FC%3A%5CDocuments+and+Settings%5CAdministrator%5CLocal+Settings%5CTemporary+Internet+Files%5CContent.IE5%5CECSFNTNT%5C1112254132_828193240%5B1%5D.jpg)
如图,在三角形ABC中,∠C=2∠A,AC=2CB,求证∠B=90°图片链接:file://C:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files\Content.IE5\ECSFNTNT\1112254132_828193240[1].jpg
如图,在三角形ABC中,∠C=2∠A,AC=2CB,求证∠B=90°
图片链接:file://C:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files\Content.IE5\ECSFNTNT\1112254132_828193240[1].jpg
如图,在三角形ABC中,∠C=2∠A,AC=2CB,求证∠B=90°图片链接:file://C:\Documents and Settings\Administrator\Local Settings\Temporary Internet Files\Content.IE5\ECSFNTNT\1112254132_828193240[1].jpg
虽然看不见图,我也能帮你解, 做角C的角平分线,交AB于点E ,因为角C=2角A,所以,角ACE=角A,所以AE=CE,过E点做AC的垂线,交AC于点D,因为AE=CE,所以AD=DC(等腰三角形三线合一),因为AC=2BC,AC=2DC,所以DC=BC,应为CE为角C的角平分线,所以角ACE=角ECB,CB=CD,CE=CE,所以三角形DCE与三角形BCE全等,所以角B=角EDC=90°