The formula for the perimeter of the sector of a circle is 

In the given figure, O is the centre of the circle and P, Q and R are points on the circumference.

The value of x is _____ degrees.

One-half of the whole arc of a circle is called a _____.

In the figure below, if $△\mathrm{ABC}$ is an equilateral triangle, then shaded area is equal to

A continuous piece of a circle is _____ of the circle.

The angle subtended by an arc of a circle at the centre of the circle is called the _____ subtended by the arc. (angle / arc)

The shaded portion $\mathrm{CMD}$ is enclosed by two radii and the arc $\mathrm{DM}$. It is called a _____ of the circle.

In the adjoining figure $\mathrm{O}$ is the centre of the circle. $\angle$_____ is the central angle subtended by the arc $\stackrel{⏜}{DB}$. $\left(AOD/ DOB/ AOB\right)$