Answer:
Therefore,
ΔABD ~ ΔACB by Angle-Angle Similarity Postulate
AB is 8 unit.
Explanation:
Given:
∠ABD ≅ ∠BCD
AD = 4
DC = 12 Therefore AC =AD + DC = 4 +12 =16
AC =16
To Find:
Similar Triangles
AB =?
Solution:
In ΔABD and ΔACB
∠ABD ≅ ∠ACB ……….{Given}
∠ A ≅ ∠ A .……..{Reflexive Property}
ΔABD ~ ΔACB ….{By Angle-Angle Similarity Postulate}
If two triangles are similar then their sides are in proportion.
Substituting the values we get

Therefore,
ΔABD ~ ΔACB by Angle-Angle Similarity Postulate
AB is 8 unit.