26.數(shù)學(xué)活動(dòng)課上,同學(xué)們用矩形紙片折疊作特殊的角.操作如下:
操作一:對(duì)折矩形紙片ABCD,使AD與BC重合,得到折痕EF,把紙片展平;
操作二:再一次折疊紙片,使折痕經(jīng)過(guò)點(diǎn)B,得到折痕BM,點(diǎn)A的對(duì)應(yīng)點(diǎn)為點(diǎn)N,把紙片展平,連接MN,BN.
(1)如圖1,當(dāng)點(diǎn)N落在EF上,直接寫(xiě)出BM和MN的數(shù)量關(guān)系.
(2)如圖2,當(dāng)AB=BC時(shí),延長(zhǎng)MN交CD于點(diǎn)P.
①求證:點(diǎn)P在∠NBC的平分線上;
②若AB=8cm,CP=3cm,求AM的長(zhǎng).