9th Class Mathematics Mensuration Circle

Circle

Category : 9th Class

Circle

We know that circle is locus of a point which moves in plane in such way that its distance from a fixed point is always constant. In this section we will emphasis on sectors, segment etc.

Sector of a Circle

The region enclosed by an arc of a circle and its two bounding radii, called sector of the circle.

In the above given figure. OABC is a sector of the circle with centre 0. Here AC is the minor arc therefore, OABC is the minor sector and other plane sector is the major sector.   Segment A segment of a circle is the region bounded by an arc and a chord. The segment containing minor arc is called a minor segment. While the segment containing the major arc is the major segment. The centre of the circle lies in the major segment.

Arc

A continuous piece of a circle is called an arc of the circle. In the figure given y below AB is an arc of a circle with centre O, denoted by $\overset\frown{AB}$. In the figure given I below $\overset\frown{ACB}$ is the minor arc and $\overset\frown{ADB}$ is the major arc.

Central Angle

An angle subtended by an arc at the centre of a circle is called central angle. In the figure given below of a circle with center 0 central angle of $\overset\frown{AB}=\angle AOB=\theta$. If $\theta <180{}^\circ$ then the arc AB is called the minor arc and the arc BA is called the major arc.

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