∠CAO+∠AOC+∠OCA=180° <=>
∠CAB/2 +∠AOC +∠BCA/2 =180° <=>
∠CAB+∠BCA = 2(180°-∠AOC)
∠CAB+∠ABC+∠BCA=180° <=>
∠ABC= 180°-(∠CAB+∠BCA) <=>
∠ABC= 180°-2(180°-∠AOC) = 2(∠AOC-90°)
∠ABC= 2(124°-90°) =68
∠AOC=124°
