Here, we have a special triangle that is 30^(∘) - 60^(∘) - 90^(∘). To find AB which is equal to DC, we can use the trigonometric ratio tan30^(∘).
tan 30^(∘)= AD/DC ⇔ tan 30^(∘)=1/sqrt(3)
⇓
AD/DC=1/sqrt(3)
Let's substitute AD=8 in the identity and use cross multiplication to find DC.