CIRCLE
Boundary rope of a cricket ground
Bangle
Coins
Ball
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Let us see some examples of circle from day-to-day life.
Of these 4 examples,
2 are wrong
Why are these
examples wrong ?
For this, let us
understand the
definition of circle
CIRCLE
O
Circle is the set of points in a given plane
?
A
4 cm
B
4 cm
C
4 cm
D
4 cm
E
4 cm
All these points are equidistant from a fixed point O
which are at a fixed
distance from a fixed point.
This fixed distance is called a radius
Can any set of points in plane be called as a circle ?
No
What can you say about OA, OB, OC, OD and OE
OA = OB = OC = OD = OE
Each of these points here satisfy a condition
Now, let us understand..
CIRCLE
A
radius
C
D
A segment joining two distinct points on a circle is called a chord.
chord
O
How many such radii can we draw in a circle ?
Infinite
What do we get ?
A segment
Now let us understand few more elements of circle
Let us consider 2 distinct points C and D
Join them
How many chords can we draw in a circle ?
Infinite
CIRCLE
Such a segment is called a CHORD
A
radius
C
D
P
Q
O
Now, let us draw a chord passing through centre of the circle
Such a chord is called a diameter
diameter
A chord passing through the centre of the circle is called a diameter.
How many such diameters can we draw in a circle ?
Infinite
chord
CIRCLE
A
radius
C
D
chord
P
Q
O
diameter
M
N
l
Such a line is called a
SECANT
secant
A line intersecting a circle in two distinct points is called a secant.
Note : A secant always contains a chord
Let us draw a line intersecting circle in two distinct points
CIRCLE