144. a) 2x+50°+6x+x+40°=360°
9x+90°=360° m(AoB)=60°+50°=110°
9x=270° m(BOC)=180°
x=30° m(COA)=70°
b) m(AOB):2=110:2=55°------m(MOB)
m(AOC):2=70÷2=35°--------m(MOC)
55°+35°=90°______ UNGHI DREPT
SAU
m(AOB)+m(AOC)=m(BOC)
m(AOB)÷2 + m(AOC):2=m(Boc):2=180°:2=90°
