已知:E是正方形ABCD的AB边延长线上一点,DE交CB于M,MN∥AE.求证:MN=MB.
证明:因为正方形ABCD,所以AE∥CD
因为MN∥AE,所以MN∥CD
所以MN:CD=EM:ED,BM:AD=EM:ED
因为在正方形里CD=AD
所以MN=BM.
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