In the introductory video on circles, we shall look at the basic terms associated with circles.
A circle is a closed curve drawn such that any point on the curve is equidistant from a fixed point. This fixed point is called the centre of the circle and the distance from the centre to any point is called the radius of the circle.
The difference between a circle and a sphere is of dimension. A circle is a two- dimensional figure which means that it has area and perimeter. On the other hand a sphere is a three-dimensional figure and has area, perimeter and volume.
Diameter is a straight line passing through the centre of the circle and joining two points of the circle. It is double the length of the radius.
A chord is a point joining two points on the circumference of a circle. The diameter is the largest chord in a circle.
A secant is a line intersecting a circle at two distinct points and extending outside the circle also.
A line that touches the circle at only one point is a tangent to the circle.
An arc is a segment of a circle. It may be minor or major depending on its length. In the circle given, ADB is the minor arc while the remaining portion is the major arc.
The area formed by an arc and the two radii at the two end points of the arc is called a sector. In the circle given, the shaded figure AOB is called the minor sector of the circle.