Răspuns:
∡AOB = alungit = 180°
∡AOC = 30°
∡BOD = 120°
∡BOC = 180° - ∡AOC = 180° - 30° = 150°
∡AOD = 180° - ∡BOD = 180° - 120° = 60°
∡DOC = ∡AOC + ∡AOD = 30° + 60° = 90°
∡AOM = ∡AOC + ∡COM = 30° + 60° = 90°
∡BOM = 180° - ∡AOM = 180° - 90° = 90°
∡AOM = ∡BOM
