20/07/13 20:52:00 nRP7fpY9.net
・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,