A circle is defined as the set of all points in a plane that are equidistant from a fixed point called the center. The diameter is the longest chord that passes through the center. An arc is a piece of the circle between two points, while the circumference is the length of the entire circle. A sector is the region between an arc and the two radii joining the center to the endpoints of the arc.

2. # CirCle ~ The ColleCTion of all The
poinTs in
a plane, whiCh are aT a
fixed
disTanCe from a fixed poinT
in The
plane, is Called a CirCle.

4. Circle – set of
all points
_________ from
a given point
called the _____
of the circle.
C
Symbol:
equidista
nt
cente
r
C

5. No points of intersection (same center)
Same center
but different
radii

6. # Diameter~ The chord which passes
through the center of the
circle is called Diameter.
Diameter is longest cord of
circle.
# Arc ~ A piece of circle between two
points is called Arc.

7. # Circumference ~ The length of the
complete circle is called
Circumference.
# Sector ~ The region between an arc and
the two radii, joining the center
to the end points of the arc is
called a Sector.

8. # Theorems~
1 Equal chords of a circle subtend equal angle at the center.
2 If the angle subtended by the chords of circle at the center
are equal, then the chords are equal.
3 The perpendicular from the center of a circle to a chord
bisect the chord.

9. # Theorems~
4 The line drawn through the center of a circle to bisect a
chords is perpendicular to the cord.
5 There is one and only one circle passing through three
given non-collinear points.
6 Equal chords of a circle {or of congruent circle} are
equidistant from the center {or
centre}.

10. # Theorem~
7 Chords equidistant from the center of a circle are equal
in length.
8 The angle subtended by an arc at the center is double the
angle subtended by it at any point on the remaining part
of the circle.
9 Angles in the same segment of a circle are equal.

11. # Theorem~
10 If a line segment joining two points subtends equal angle
at two other points lying on the same side of the line
segment the four points lie on a circle.
11 The sum of either pair of opposite angle of a cyclic
quadrilateral is 180`.
12 If the sum of a pair of opposite angle of quadrilateral is
180`, the quadrilateral is
cyclic.