PM=BD+PN利用3个角都相等的原理证明△拆此BCD∽△PCN∽△PBM得旅兆迅:BD/PN=BC/CPPM/PN=BP/CP=(BC+CP)/猜液CP=BC/CP +1=BD/PN +1化简得:PM=BD+PN
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PM=BD+PN