Page 296 - Math_Genius_V1.0_C7_Flipbook

D:\Surender Prajapati\CBSE_ICSE_Book_New\CBSE\Grade-7\Math_Genius-7\Open_File\13_Chapter\13_Chapter
\ 15-Nov-2024 Surender Prajapati Proof-5 Reader’s Sign _______________________ Date __________

Circle

A circle is a geometrical figure consisting of all the points in a plane that are Q
at a fixed distance from a given point in the same plane. Centre
Here, in the given figure, O is the fixed point, and it is called the centre of O Radius M
circle, and OM is the radius of the circle.
P
Let us take two other points P and Q on the circle and join them by a straight
line passing through the point O, the centre of the circle. This is called the diameter of the circle.
The diameter of the circle is the twice of its radius.
Diameter Boundary of a circle is a curved
\ Diameter = 2 × radius or Radius = Note: line, we cannot measure it with
2 the help of a ruler.
Circumference of a Circle

activity
• Take a cutout of a circle and place a string or a thread along the boundary of circular cutout.

• Place the string or thread on the ruler and measure its length.
• The length of the string or thread will give the measure of the circumference of the circle.

The circumference of a circle is the measurement
of the boundary of the circle. maths fun
Thus, the perimeter of a circle is called the Take a bottle cap, a bangle or any other
circumference of the circle. circular object and find the circumference
It is measured in units such as cm, m, etc. of the object by using a piece of thread.

There is a relationship between the diameter and the circumference of a circle.
That is, if we take circles with different radii and find their circumference then, in each case, the
Circumference(C)
value of is approximately same and slightly more than 3.
d
Diameter()
So, we can say that, the ratio of the circumference to the diameter of a circle is a constant and
this constant is called p (pi). It is a Greek alphabet letter and its approximate value is 22 or 3.14.
7

Mathematics-7 294