3. Circle is the collection of points in a plane that are all the
same distance from a fixed point.
The fixed point is called the center.
4. The diameter starts at one side of the circle, goes
through the center and ends on the other side.
A line segment joining the center to any point on
the circle is called radius.
5. A line joining any pair of points on a circle, is
called a chord of the circle.
The longest chord DB, is called the diameter of
the circle.
AB,DB,CD are the chords of the circle
6. The perpendicular from the center of a circle to a
chord, passes through the midpoint of the chord.
7. Prove that in a circle , chords of equal length are at equal
distance from the center ?
AE,BF are chords of equal length and OC, OD
are perpendicular from the center O of the
circle to these chords.
We have ,AC = ½ AE and BD = ½ BF
Since ,AE = BF. We get , AC = BD
8. From the right angled triangle OAC, OBD ,
We get, OC2 = OA2 – AC2
OD2 = OB2 – BD2
Since, OA = OB (radius )
AC = BD
,
We get, OC2 = OD2
And so OC = OD
