下列命題中,真命題是( )
A.矩形的對角線相互垂直
B.順次連結(jié)四邊形各邊中點所得到的四邊形是矩形
C.等邊三角形既是軸對稱圖形又是中心對稱圖形
D.對角線互相垂直平分的四邊形是菱形
答案:解:(1),
,,
.······························· 1分
四邊形是平行四邊形,
.······························· 2分
在和中,
,,,
.···························· 3分
(2)解法一:,
.······························· 4分
四邊形是平行四邊形,
.
.
.····························· 5分
四邊形是矩形.·························· 6分
解法二:連接.
,
.
.···························· 4分
在和中,
,,,
.
.······························· 5分
四邊形是平行四邊形,
四邊形是矩形.·························· 6分
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