In Fig. 2, a quadrilateral ABCD is drawn to circumscribe a circle, with centre O, in such a way that the sides AB, BC, CD and DA touch the circle at the points, P, Q, R and S respectively. Prove that AB+CD=BC+DA.

In Fig. 2, a quadrilateral ABCD is drawn to circumscribe a circle, wit

1.	In Fig. 2, a quadrilateral ABCD is drawn to circumscribe a circle, with centre O, in such a way that the sides AB, BC, CD and DA touch the circle at the points, P, Q, R and S respectively. Prove that AB+CD=BC+DA.
Answer» In Fig. 2, a quadrilateral ABCD is drawn to circumscribe a circle, with centre O, in such a way that the sides AB, BC, CD and DA touch the circle at the points, P, Q, R and S respectively. Prove that $A B + C D = B C + D A$ .