A circle is the locus of a point which moves in a plane in such a way that its distance from a given fixed point is always constant.
The fixed point is called the center and the constant distance is called the radius of the circle.
Terms related to a circle: -
Radius is a line segment joining the center and a point on the circle is called its radius.
Diameter is a chord of a circle passing through the Centre of the circle.
A diameter is the longest chord of a circle.
Diameter = 2 x radius
Chord of a circle is a line segment joining any two points on the circle.
Secant: - A line which intersects a circle in two distinct points is called a secant of the circle.
Circumference: - The perimeter of a circle is called its circumference.
Circumference = 2 π r and
Area of a circle = π r^2
Where,
r= radius of the circle and π = 22 / 7
Example: - Find the radius of the circle if the diameter of the circle is 28 cm.
Solution: -
Diameter = 2 x radius
Radius = Diameter / 2
= 28 / 2
= 14 cm.
Example: - A circular field has the radius of 7 cm. Find the perimeter and area of the field.
Solution: -
Circumference = 2 π r
= 2 * (22 / 7) * 7
= 44 cm
Area of a circle = π r^2
= (22/7) * 7^2
=154 cm^2