In the given figure, a circle is inscribed in the quadrilateral ABCD. Given AB=6cm, BC=7cm and CD=4cm. Find AD.
∵ Tangent segments drawn from an external point to a circle are equal to
∴ BP = BQ
CR = CQ
DR = DS
AP = AS
⇒ BP + CR + DR + AP = BQ + CQ + DS + AS
⇒ AB + DC = BC + AD
∴ AD = 10 - 7 = 3 cm