In the given figure, O is the center of a circle. AB is the side of a square and BC is side of a regular hexagon. Also arc AD = arc CD. Angle DOC is equal to :

1. 150°

2. 105°

3. 130°

4. 210°

In the given figure, O is the center of the circle and angle OAB = 55°, then angle ACB is equal to :

1. 55°

2. 35°

3. 70°

4. 30°

In the given figure, O is the center of the circle, chords AB, CD and EF are equal whereas chords BC, DE and FA are separately equal. The angle AOC is equal to :

1. 80°

2. 100°

3. 90°

4. 120°

In a cyclic-trapezium, the non-parallel sides are equal and the diagonals are also equal. Prove it.