In ΔABC BC = BA(Given) ⇒ ∠BAC =∠BCA......(1) Remember: Equal sides have equal anglesopposite to them. In ΔADC, CD > AD (Given) Remember:In a triangle, greater side has greater angle opposite to it. ⇒ ∠CAD > ∠ACD ......(2) Adding (1) and (2), we have ∠BAC+∠CAD>∠BCA+∠ACD ⇒ ∠BAD > ∠BCD