Triangle OAB is inscribed in a circle. O is the centre of the circle. A and B are on the circumference of the circle.

Triangle OAB is an isosceles triangle, with OA = OB.

Triangle ABC is inscribed in a circle. A, B and C are on the circumference of the circle. AC passes through O, the centre of the circle.

Triangle ABC is a right-angle triangle, with Ð ABC = 90°.

ABCD is a rhombus.

Triangle ABD is an isosceles triangle, with AB = AD.