A circle is a curve joining a set of points which are at same distance from a fixed point. Here, the fixed point is called the center of the circle and the fixed distance is called the radius of the circle.
Here is the terminology regarding a circle.
Here O is the center of the circle. r is the radius of the circle.
Here, we can notice that, AO = OB = r.
Chord of the circle:
A chord is a line which joins any two points on the circle.
In the above figure, ED is a chord.
Diameter of the circle:
The diameter is the largest chord of the circle. The diameter always passes through the center of the circle and its length is twice the length of the radius.
In the above figure, AB is a diameter of the circle and AB = 2r.
Tangent of a circle:
A tangent of a circle is a line which touches the circle at only one point. i.e A chord can become a tangent if its starting and ending points become same.
In the above figure, FG is a tangent which passes through the point B , which lies on the circle.
Arc of a circle:
The arc of a circle is the part of the circle which lies between any two points on the circle.
In the above figure BC is an arc of the circle.
Sector of a circle:
The sector of a circle is the part of area of the circle lying between the arc and the radii.
In the above figure OCB is a sector.
Central angle of a circle:
It is the angle formed by any two radii of the circle.
In the above figure, ∠COB is a central angle.
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