(i) Here, ABCD is a parallelogram and diagonal AC bisects ∠A. ∴ ∠DAC=∠BAC ---- ( 1 ) Now, AB∥DC and AC as traversal, ∴ ∠BAC=∠DCA [ Alternate angles ] --- ( 2 ) AD∥BC and AAC as traversal, ∴ ∠DAC=∠BCA [ Alternate angles ] --- ( 3 ) From ( 1 ), ( 2 ) and ( 3 ) ∠DAC=∠BAC=∠DCA=∠BCA ∴ ∠DCA=∠BCA Hence, AC bisects ∠C. (ii) In △ABC, ⇒ ∠BAC=∠BCA [ Proved in above ] ⇒ BC=AB [ Sides opposite to equal angles are equal ] --- ( 1 ) ⇒ Also, AB=CD and AD=BC [ Opposite sides of parallelogram are equal ] ---- ( 2 ) From ( 1 ) and ( 2 ), ⇒ AB=BC=CD=DA Hence, ABCD is a rhombus.