28.蘇科版教材八年級(jí)下冊(cè)第94頁(yè)第19題,小明在學(xué)過(guò)圓之后,對(duì)該題進(jìn)行重新探究,請(qǐng)你和他一起完成問(wèn)題探究.
【問(wèn)題提出】如圖1,點(diǎn)E,F(xiàn)分別在方形ABCD中的邊AD、AB上,且BE=CF,連接BE、CF交于點(diǎn)M,求證:BE⊥CF.請(qǐng)你先幫小明加以證明.
【問(wèn)題探究】小明把原問(wèn)題轉(zhuǎn)化為動(dòng)點(diǎn)問(wèn)題,如圖1,在邊長(zhǎng)為6cm的正方形ABCD中,點(diǎn)E從點(diǎn)A出發(fā),沿邊AD向點(diǎn)D運(yùn)動(dòng),同時(shí),點(diǎn)F從點(diǎn)B出發(fā),沿邊BA向點(diǎn)A運(yùn)動(dòng),它們的運(yùn)動(dòng)速度都是2cm/s,當(dāng)點(diǎn)E運(yùn)動(dòng)到點(diǎn)D時(shí),兩點(diǎn)同時(shí)停止運(yùn)動(dòng),連接CF、BE交于點(diǎn)M,設(shè)點(diǎn)E,F(xiàn)運(yùn)動(dòng)時(shí)間為t秒.
(1)如圖1,在點(diǎn)E、F的運(yùn)動(dòng)過(guò)程中,點(diǎn)M也隨之運(yùn)動(dòng),請(qǐng)直接寫(xiě)出點(diǎn)M的運(yùn)動(dòng)路徑長(zhǎng)
cm.
(2)如圖2,連接CE,在點(diǎn)E、F的運(yùn)動(dòng)過(guò)程中.
①試說(shuō)明點(diǎn)D在△CME的外接圓⊙O上;
②若①中的⊙O與正方形的各邊共有6個(gè)交點(diǎn),請(qǐng)直接寫(xiě)出t的取值范圍.