Question

Define circumference of circle.

Answer 1

Circumference of Circle:
Perimeter of closed figures is defined as length of its boundary. When it comes to circles, perimeter of circle is given a different name. It is called circumference of circle. To define the circumference of circle, knowledge of a term known as 'pi' is required. Consider the circle shown in the fig. 1, with center at 0 and radius r.



The circumference of the above circle is equal to the length of its boundary. The length of rope which wraps around its boundary perfectly will be equal to its circumference.
$\pi$, read as 'pi' is defined as the ratio of circumference of a circle to its diameter. This ratio is same for very circle. Consider a circle with radius 'r' and circumference 'C'. For this circle
$\pi =\frac{circumference}{Diameter}$
$\pi =\frac{C}{2r}$
$C=2\pi r$