Basic Definition and Terms related to Circle: Class 10th NCERT Notes

Areas Related to Circles

  • A circle is a shape consisting of all points in a plane that is a given distance from a given point, the centre; i.e it is the curve drawn out by a point that moves in a plane so that its distance from a given point is constant.

Center | Centre (Circle)

Some of real-world examples are: Cycle wheels, round cake, bangles, round pizza, Coins etc

Coins
The coin has a circular shape

Oggi's Pizza Express Bicycle, bike, biking, cycle, cycling, wheel icon

 

After knowing the concept of circle let’s get into some of the important Terminology of the circle:

Term Definition
Annulus a ring-shaped object, the region bounded by two concentric circles.
Arc any connected part of a circle. Specifying two endpoints of an arc and a centre allows for two arcs that together make up a full circle.
Centre the point equidistant from all points on the circle.
Chord a line segment whose endpoints lie on the circle, thus dividing a circle into two segments.
Circumference the length of one circuit along the circle, or the distance around the circle.
Diameter a line segment whose endpoints lie on the circle and that passes through the centre
Disc the region of the plane bounded by a circle.
Radius a line segment joining the centre of a circle with any single point on the circle itself
Sector a region bounded by two radii of equal length with a common center and either of the two possible arcs, determined by this center and the endpoints of the radii.
Segment a region bounded by a chord and one of the arcs connecting the chord’s endpoints. The length of the chord imposes a lower boundary on the diameter of possible arcs.
Secant an extended chord, a coplanar straight line, intersecting a circle in two points.
Semicircle one of the two possible arcs determined by the endpoints of a diameter, taking its midpoint as centre.
Tangent a coplanar straight line that has one single point in common with a circle (“touches the circle at this point”).

File:CIRCLE LINES.svg File:Circle slices.svg

 

CD General Computer Disc Disk Music Data IT Secondary Bw RGB Illustration https://upload.wikimedia.org/wikipedia/commons/thumb/e/e9/Semicircle.svg/1024px-Semicircle.svg.png

Above figures describe what exactly each terminology look like.

Now let us get into detailed concepts of each terminology of the circle starting with Perimeter and Area of a Circle.

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