作业帮2,3问
来源：学生作业帮助网 编辑：作业帮 时间：2024/07/21 01:12:02
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2,3问
2,3问
2,3问
2.连接DG,CG = CD = 3根2 / 2 (1已求得)
角CGD = 角CDG = 角A = 角GEF = 45度..角CGE = 角GEA
则角DGE = 角FEA.三角形GDE.EAF.相似.
DE/ GD = AF/ AE ===== x / 3 = y/(4根2 - x) ==== y = x(4根2 - x)/3
3.由于相似,AEF 是等腰三角形,也就是DGE是等腰三角形,有3种情况,
a.AF= EF.也就是 GE = DE,此时,此时,GE垂直AD.EF垂直AB,.重叠部分是GBFE,
S = S梯形GBAE - S三角形AEF = 9/2 - 2 = 5/2
b .EF = AE .此时,DG = GE,角DGE= 角FEA = 90度,x =DE =3根2,时
S = S三角形AEF = 1
c.AF = AE,也就是 DE =DG = 3 时,AF = AE =AD- DE = 4根2 - 3 < 3
由于AE = AF ,则折叠后的图形,A'EFA,为菱形,A'F//AE.
则重叠面积 S = S三角形AEF = AE^2sin 45 / 2
这题是不是BG=AB=根号2
不好意思