The angle in a semicircle measures

In the given figure, AB is a chord of a circle with centre O and BOC is a diameter. If OD ⊥ AB such that OD = 6cm then AC = ?

An equilateral triangle of side 9 cm is inscribed in a circle. The radius of the circle is

Angles in the same segment of a circle area are

In the given figure, ΔABC and ΔDBC are inscribed in a circle such that ∠BAC = 60° and ∠DBC = 50°. Then, ∠BCD = ?