GEOMETRY
Chapter:Circle Terminology
What is Circle?
• A circle is a two-dimensional figure formed
by a set of points that are at a fixed distance
(radius) from a fixed point (center) on the
plane. The fixed point is called the origin or
center of the circle and the fixed distance of
the points from the origin is called
the radius. Observe the following figures to
see the basic parts of a circle, the center,
the radius, and the diameter of a circle.
1) Radius
A
• The segment joining
the center of a circle to
a point on the circle.
O
• Example: OA is the
radius and O is the
center of the cercle
2) Chord
• A segment joining two
points on a circle
B
• Example 01: AB
A
C
B
• Example 02: AB
C
A
3) Diameter
• A chord that passes
through the center of a
circle.
A
O
• Example: AB
B
4) Secant
A
• A line that intersects
the circle at exactly
two points.
C
O
• Example 01: AB
D
B
A
C
• Example 02: AB
O
D
B
5)Tangent
B
C
• A line that intersects a
circle at exactly one
point.
A
• Example: AB
6) Central Angle
A
• An angle whose vertex
is at the center of a
circle.
B
• Example: Angle ABC
C
7)Inscribed Angle
B
A
C
• An angle whose vertex
is on a circle and
whose sides are
determined by two
chords.
• Example: Angle ABC
8) Arc
• A figure consisting of
two points on a circle
and all the points on
the circle needed to
connect them by a
single path.
• Example: arc AB
B
A