A Circle

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


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