Question : $\mathrm{O}$ is the centre of a circle and $\mathrm{A}$ is a point on a major arc $\mathrm{BC}$ of the circle. $\angle \mathrm{BOC}$ and $\angle \mathrm{BAC}$ are the angles made by the minor arc $\mathrm{BC}$ on the centre and circumference, respectively. If

Question : In $\Delta ABC$, the external bisector of the angles, $\angle B$ and $\angle C$ meet at the point $O$. If $\angle A = 70^\circ$, then the measure of $\angle BOC$:

Question : The angle subtended by an arc at the circumference of the circle is 55°. Find the angle subtended by it at the centre.

Question : The angle subtended by a chord on the major arc of the circle is 50°. What is the angle subtended by the same chord on the centre of the circle?

Question : Minor arc $BC$ subtends $\angle BAC$ and $\angle BDC$ at points $A$ and $D$, respectively, on the circumference of the major sector of the circle with centre $O$. What is the value (in degrees) of $(\angle ABC+\angle ACB)$, if $\angle BDC=73^{\circ}?$