This document defines key terms and formulas related to circles. It explains that a circle is a closed, round geometric shape where all points are equidistant from the center point. It then defines parts of a circle like the radius, diameter, chord, secant, arc, tangent, sector, and segment. Finally, it provides the formulas for calculating the circumference and area of a circle, which both relate to the radius and use the value of pi.

1. MATHEMATICS

2. What is a Circle?
Parts of a Circle
Formulas

3. What is a Circle?
A closed, round geometric figure in
which the set of all the points in the
plane is equidistant from a given
point called ‘center’.
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5. Parts of a Circle
 Radius – The line that joins the center of the circle
to the outer boundary. It is usually represented by ‘r’
or ‘R’. The plural of radius is called radii.
 Diameter – The line segment whose endpoints lie
on the circle and that passes through the center. Its
length is twice the length of a radius. It is
represented by as -‘d’ or ‘D’.
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6. Parts of a Circle
 Chord – The line segment whose endpoints lie on
the circle, thus dividing a circle into two regions. The
diameter is the longest chord of a circle.
 Secant – An extended chord that cuts the circle at
two distinct points.
 Arc – The connected section of the circumference of
a circle.
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7. Parts of a Circle
 Tangent – A line that touches the circumference of
a circle at a point.
 Sector – A region bounded by two radii of equal
length with a common center.
 Segment – The segment of a circle is the region
bounded by a chord and the arc subtended by the
chord.
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8. Formulas
 Circumference
- Also known as the perimeter, it is the total
distance covered around the circle. The
formula is given below:
 Circumference (C) = 2πr, here r = radius,
and π = 3.141 = 22/7

9. Formulas
 Area
- It is the total space enclosed inside the
boundary of the circle. It is also known as the
‘surface area of the circle’. The formula is
given below:
 Area (A) = πr2, here r = radius, and π = 3.141
= 22/7