4: 53°=> 90°-37°=53°;
5: 129°=> 180°-51°=129°;
6: Rezolvarea problemei:
AOB+BOC=120°;
AOB=4×BOC;
4BOC+BOC=120°;
5BOC=120/:5;
BOC=24°;
AOB=4BOC=>AOB=4×24°=96°;
96°-24°=72°.
SUBIECTUL III: