如图所示，[tex=3.143x1.214]BypMH6cWAb0x8gikbHmOkm8G6z9CQ+Rgr92Svssi5/0=[/tex]中的点[tex=0.857x1.0]SgBD8u1wdBgpRP8N7rG5Xg==[/tex]，[tex=0.786x1.0]EQXwRT/L3tg9/NvDMlGuPg==[/tex]，[tex=0.643x1.0]gSWKSAtjuAhig1ykYkQFSA==[/tex]分别为边[tex=1.5x1.0]gk/gZjx6JE3zHuixQGLyeQ==[/tex]，[tex=1.5x1.0]WLtGedh8dmf9ZT2t3nbJTQ==[/tex]与[tex=1.571x1.0]qhPZqOIdFzeJqSPqua6fCw==[/tex]上的中点，设中线[tex=1.643x1.0]irC544DtxjnZszduGCT79w==[/tex]，[tex=1.5x1.0]hnmDtGwaOChMIsqwAigF+A==[/tex]交于[tex=0.786x1.0]XhVNsLJz3AkjM19LvAbO7w==[/tex]，下证中线[tex=1.357x1.0]GNZfQpipFssDuO1W+MHAmg==[/tex]经过[tex=0.786x1.0]XhVNsLJz3AkjM19LvAbO7w==[/tex]点，即证明[tex=0.714x1.0]zAR8JLTji7MW5PnI4azq+Q==[/tex]，[tex=0.786x1.0]XhVNsLJz3AkjM19LvAbO7w==[/tex]，[tex=0.643x1.0]gSWKSAtjuAhig1ykYkQFSA==[/tex]三点共线.[img=221x156]1789b0a0d188b41.png[/img]根据题意得[p=align:center][tex=25.0x7.643]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[/tex]又由[p=align:center][tex=8.857x2.357]JXEZtHVD9o3tldNRYIh3SOI1ZiKRzyDcaYwjLP+3uNo6MHSpmHMzC0P+cOnc6sTw960b+iaBulLzg+Xjri58aDRvvqN85o7HOFXTapr5dPQVQUK3VccXbnYMR/poYwxI[/tex]从而 [tex=4.857x1.643]dCIjCN7Tx1bbApSKK5aKBOnBISUInut4ChZqs2MjKlfbF37whM128i+yUmueMN1X[/tex]，即[tex=0.714x1.0]zAR8JLTji7MW5PnI4azq+Q==[/tex]，[tex=0.786x1.0]XhVNsLJz3AkjM19LvAbO7w==[/tex]，[tex=0.643x1.0]gSWKSAtjuAhig1ykYkQFSA==[/tex]三点共线.