S△OGC=S△OBC/3
S△OEC=S△OAC/3
S◇OECG
=S△OGC+S△OEC
=(S△OBC+S△OAC)/3
=(S△EBC+S△GAC-S◇OECG)/3
=(2S△ABC/3-S◇OECG)/3
3S◇OECG=2S△ABC/3-S◇OECG
S◇OECG=S△ABC/6=1/6
S△OGC=S△OBC/3
S△OEC=S△OAC/3
S◇OECG
=S△OGC+S△OEC
=(S△OBC+S△OAC)/3
=(S△EBC+S△GAC-S◇OECG)/3
=(2S△ABC/3-S◇OECG)/3
3S◇OECG=2S△ABC/3-S◇OECG
S◇OECG=S△ABC/6=1/6