pada gambar berikut, panjang busur AB = 30 cm, AOB = 40°

busur CD = 60/40 x 30
                 =3/2 x 30
               = 45 cm
jawab.B

CD

→ sudut COD / sudut AOB × 30 cm
→ 60/40 × 30cm
→ 60/4 × 3
→ 180/4 = 45 cm