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Circle and its Parts

CIRCLE:- It is the path traversed by locus of all points equidistant from a point.

Parts of Circle:-

circle and its parts

Center: - The fixed point O is called the center.

Radius: - The fixed distance OA is called radius. All radii of a circle are equal.

Diameter: - A line segment AOC passing through the center of a circle, and having its end points on the circle on the circle is called the diameter of the circle. Diameter= 2 x radius. All diameters of a circle are equal.

The diameters of a circle are concurrent. The center is the point common to all diameters.

Chord: - A line segment ED with its end-points lying on a circle is called a chord of the circle. Diameter is the longest chord of the circle.

Semi-circle: - A diameter of a circle divides the circle into two parts; each part is called a semi-circle.

Circumference: - The perimeter of the circle is called its circumference.

Arc: - Two points of a circle divide the circle into two parts; each part is called an arc of the circle.A piece of a circle cut between two points is called an arc. There are two, one longer and other smaller. The larger one is called the major arc PQ and the smaller one is called minor arc PQ. The minor arc PQ is also denoted by arc PQ and the major arc PQ by PRQ. When P, Q is ends of diameter, then both arcs are equal and each is called a semicircle

Segment: - A region in the interior of a circle enclosed by a chord and an n arc is called a segment of the circle.. There are two types of segments, major segment and minor segment. Like segments you find that minor arc corresponds to minor sector. And major arc corresponds to major sector. The region OPQ is the minor sector and remaining part of the circular region is the major sector

Sector: - A region in the exterior of the circle enclosed by an arc on one side and a pair of radii on the other two sides is called a sector.

Examples on Circle Parts

Example: From the figure identify

circle and its parts

  1. the center of the circle
  2. three radii
  3. a diameter
  4. a chord
  5. two points in the interior
  6. a point in the exterior
  7. a sector
  8. a segment

solution: The parts are:

  1. O is the center of the circle.
  2. OA, OB and OC
  3. AC
  4. ED is a chord of circle
  5. points O and P are in the interior of the circle
  6. point Q in the exterior of the circle
  7. OAB is a sector of circle
  8. shaded region in the interior of a circle enclosed by a chord ED.

Example: (a) Is every chord of a circle also a chord?

(b) Is every chord of a circle also a diameter?

Solution: (a) Yes, a diameter is the longest chord.

(b) not always

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