ABCD is a cyclic quadrilateral. AB and DC are produced to meet at P. Which of the following statements is/are correct? I. △PAD is similar to △PBC II. ∠PAD + ∠PDA = ∠PBC + ∠PCB

In cyclic quadrilateral ABCD, exterior angle of cyclic quad equals interior opposite angle. So ∠PAD = ∠BCD's supplement related angle, and triangles PAD and PBC share angle P, with ∠PAD = ∠PCB (exterior angle = interior opposite). Thus △PAD ~ △PBC by AA similarity, so statement I is correct. Since the triangles are similar, corresponding angle sums are equal: ∠PAD + ∠PDA = ∠PCB + ∠PBC, so statement II is also correct.