Let’s do an activity to understand the basics of circle
Step1: Trace a circle on a paper using any
circular object such as a big bottle cap or a bangle and cut along the traced
Step2: Fold the cut circle into half. We will get
semicircle. Now unfold the semicircle and see the pleat formed is called the diameter
Step3: Again fold the half folded circle again
into half. We will get a quadrant. Now open the fold of quadrant. We
will see 4 pleat meeting at a common point. This point is called center of
the circle and pleats meeting at a point are called radii of the circle.
Step4: If we fold any part of the circle now. The
pleat formed is called the chord of the circle.
Step5: The length of the boundary formed after
tracing is called the circumference of the circle.
Circle - A circle is a closed curve. Points on the
border of the circle are equidistant from the center of the circle.
Radius – Radius is any line segment from center
to the edge of the circle.
radii of the circle are equidistant from the edge of the circle i.e all radius
are equal in length.
Diameter – Diameter is a line segment that starts
at one side of circle, passes through the center of the circle and touches the
other end of the circle.
= 2 x radius
Example 1: Radius = 6 cm
Diameter = 2 x 6 cm
= 12 cm
Example 2: Diameter = 18 cm
Radius = 18/2
= 9 cm
diameter of the given circle are equal in length. Each diameter is formed of
two radii. Diameter is twice the length of the radius.
Circumference - The length of the boundary of a
circle is called circumference of a circle.
Chord – Line segment joining any two points on
the edge of the circle is called chord. Diameter is longest chord of the
Arc – Any part of the circumference of the
circle is called arc.