因为O是三角形ABC的外心所以OA = OB = OC所以∠OAC = ∠OCA,∠OAB = ∠OBA ,∠OBC = ∠OCB因为∠BOC = 140°所以 ∠OBC = ∠OCB = 20°又因为 ∠OAC + ∠OCA + ∠OAB + ∠OBA + ∠OBC + ∠OCB = 180°所以∠OAC + ∠...