ada yg tau caranya...........................

sin ADE = AE/AD
sin 30 = AE/AD
1/2 = AE/10
AE = 1/2 x 10
AE = 5 cm

panjang CD = AB - 2AE
panjang CD = 18 - 2(5)
panjang CD = 18 - 10
panjang CD = 8 cm (D)