・稜長
OA = 1,　OB = 41/9,　OC = 84/13,
AB = 40/9,　AC = 85/13,　BC = 925/117,
・面積
OA⊥AB より　⊿OAB = OA･AB /2 = 20/9,
OA⊥OC より　⊿AOC = OA･OC /2 = 42/13,
OB⊥OC より　⊿BOC = OB･OC /2 = 574/39,
AB⊥AC より　⊿BAC = AB･AC /2 = 1700/117,
・体積
V(COAB) = OC･OA･AB /6 = 560/117,