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Let us recall the fundamentals of circles which we studied in previous chapters.

**Circle**:

A closed line consisting of all points on the plane that are equidistant from a given point on the plane is called a circle.

**Diameter of the circle**:

- The distance across the circle.
- The length of any chord (a straight line which connects two points on a circle) passing through the center.
- It is twice the radius.

**Diameter**\(=\) \(2 ×\) Radius \(=\) \(2r\)

**Radius of the circle**:

The radius is the distance from the center to any point on the circle.

Radius is also known as half of the diameter.

$\mathrm{Radius}=\frac{\mathrm{Diameter}}{2}$

**Area of the circle**:

The area of a circle is the number of square units inside that circle.

Area of the circle \(=\) $\mathrm{\pi}{r}^{2}$ sq. units

Here \(r\) is the radius of the circle.

**The value of the**$\mathrm{\pi}$ [pi]

**can be either**\(22/7\)

**or**\(3.14\).