a) Larc=π R *x°/180°
L AB=πR*m(AOB)°/180°
2=πR*30°/180°
R= 12/π
m(BOC)=L BC*180°/πR=5*180°/(12π/π)=900/12=75°
m(COD)=L CD*180°/πR=6*180/(12π/π)=1080/12=90°
b)R=12/π=12/3,14=3,82 cm
c) m(AOD)=360-m(ABO)-m(BOC)-m(COD)=360-30-75-90=165°
L AD= πR*m(AOD)/180°=[(12π/π)*165]/180=1980/180= 11cm