m∡MAO=m∡AOB=m∡NBO=a° (alterme interne)
m∡MAO=m∡AMO (ΔAOM isoscel, OB si ON , raze)
m∡NBO=m∡ONB (ΔBON isoscel OB,ON raze)
atunci m∡MOA=m∡NOB=180-2a°
si m∡MON=2(180-2a°) +a°=360°-3a°=mas arc "mic" MN
iar mas arc mare MN= 360°-(360°-3a°)=3a°
pt cazurile particulare date
caz 1) 360-150=210° si celalalt150°
caz 2) 360-180=180° si celalat 180°
as elegant as that!!