因为A'为BC中点,所以 S(△AA'B) = S(△AA'C) & S(△OA'B) = S(△OA'C)
同理
S(△BB'A) = S(△BB'C) & S(△OB'A) = S(△OB'C)
S(△CC'A) = S(△CC'B) & S(△OC'A) = S(△OC'B)
=>
因为 S(△AA'B) = S(△AA'C) & S(△OA'B) = S(△OA'C), 所以 S(△AOB) = S(△AOC)
同理
S(△AOB) = S(△AOC) = S(△BOC)
=> S(△OA'B) = S(△OA'C) = S(△OB'A) = S(△OB'C) = S(△OC'A) = S(△OC'B)
因此, S(△AOC) = 2 x S(△A'OC) => AO = 2 A'O
同理,S(△BOC) = 2 x S(△B'OC) => BO = 2 B'O
S(△COB) = 2 x S(△C'OB) => CO = 2 C'O