如图所示,设M是△ABC的重心,过M的直线分别交边AB,AC于P,Q两点,且AP/PB=m,AQ/QC=n,则1/m+1/n=_.
问题描述:
如图所示,设M是△ABC的重心,过M的直线分别交边AB,AC于P,Q两点,且
=m,AP PB
=n,则AQ QC
+1 m
=______.1 n
答
分别过点B,C作BE∥AD,CF∥AD,交PQ于点E,F,则BE∥AD∥CF,
∵点D是BC的中点,
∴MD是梯形的中位线,
∴BE+CF=2MD,
∴
+1 m
=1 n
+PB AP
=CQ AQ
+BE AM
=CF AM
=BE+CF AM
=1.2MD AM