Looking at the diagram above, since OA and OB are radii of the circle, then OA = OB, therefore\(AOB\) forms an isosceles triangle inside the circle. Also, note that since \(\Delta AOB\) is ...

Some trapeziums have one line of symmetry. They are called isosceles trapeziums as they have 2 sides of an equal length like isosceles triangles. A trapezium has rotational symmetry of order one.