babyhuang1983
幼苗
共回答了21个问题采纳率:95.2% 举报
过B作BE∥MA交MP的延长线于E,过C作CF∥MA交MQ的延长线于F,延长AM交BC于D.
∵M是△ABC的重心,∴AM=2MD、BD=CD.
∵BE∥MA,∴△APM∽△BPE,∴AM/BE=AP/PB=m,∴1/m=BE/AM.······①
∵CF∥MA,∴△AQM∽△CQF,∴AM/CF=AQ/QC=n,∴1/n=CF/AM.······②
①+②,得:1/m+1/n=(BE+CF)/AM.······③
∵BE∥MA、CF∥MA,∴BE∥DM∥CF,又BD=CD,∴BE+CF=2MD=AM.······④
由③、④,得:1/m+1/n=1.
1年前
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