Circle and its Parts
Introduction
Recall the basic concepts about circles that you learnt in the earlier classes.
A circle is a set of points on a plane which are at the same distance from a fixed point. The fixed point is known as the centre of the circle.
Centre of the circle. |
The radius of a circle is a line segment, with one end point at the centre of the circle, and the other on the circle.
The diameter of a circle is a line segment which passes through the centre of the circle, and has both its end points on the circle. Obviously, diameter = 2 Ã— radius.
A chord is a line segment with its end points lying on the circle. A chord may or may not pass through the centre of the circle. When it passes through the centre, it becomes the diameter. The diameter is the longest chord of a circle.
Chord |
A secant is a line passing through a circle and intersecting the circle at two points.
Secant |
A chord of a circle divides the circular region into two parts. Each part is called a segment of the circle.
The larger segment which contains the centre of the circle is called the major segment of the circle. The smaller segment which does not containing the centre is called the minor segment.
Segments of a circle |
A part of a circle is called the arc of the circle. If the arc is greater than half the circle it is called a major arc. If it is less than half a circle, it is called a minor arc.
Arc of the circle |
The perimeter of a circle is called its circumference.
The end points of the diameter of a circle divide it into two halves. Each half is called a semicircle.
Semicircle |
A sector of a circle is a region enclosed by an arc and two radii of the circle.
Sector |