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# THE BASIC CONCEPT OF CIRCLES AND SEMI-CIRCLES

Circle and semicircle are two geometrical figures in mathematics the concepts of which should be cleared to the kids to solve different geometrical problems. Here in this article, we have explained some basics of the circle and semicircle such as meaning, parts of a circle, area of circle, the circumference of a circle, and formulas of semicircle in easily understandable language.

# What is a circle in geometry?

A circle being an enclosed two-dimensional geometric figure is a collection of points that are equidistant from the given point known as the ‘center of the circle’. There are various examples of the circle that are encountered in real-life such as rings, CDs, bangles, buttons, wheels, and many more.

## Mentioning the parts of a circle:

Below-mentioned is important parts of a circle:

• Center: It is the midpoint in a circle.
• Annulus: Annulus is the region that is bounded by the two concentric circles.
• Radius: Radius is the line segment running from the center to a point on the boundary of the circle.
• Diameter: Diameter is basically two times of radius. It is the line segment passing through the center and joining the endpoints lying on the boundary of the circle.
• Chord: Chord is basically a line segment that joins the endpoints lying on the circle.
• Sector: It is the area that is bounded by two radii and an arc.
• Segment: It is basically the area that is bounded by a chord and an arc.

## What are the formulas of the circle?

There are two main formulas of a circle, one is used to calculate the area of the circle and another helps to calculate the circumference of the circle.

• Area of the circle: The area of a circle can be defined as a region that is enclosed within the circle’s boundary. It can be calculated using the below-given mathematical formula:

## Area of a Circle = π × r2

• Circumference of the circle: The circumference or perimeter of the circle can be defined as the length of the boundary of the circle. It can be calculated using the below-given mathematical formula:

# Circumference of a Circle = 2π r

## What is a semicircle in geometry?

After passing the line through the center by touching the two ends of the circle, a semicircle is formed. The radius of the semicircle can be defined as the line segment running from the center to the point on the boundary of the semicircle.

## What are the formulas of a semicircle?

There are two main formulas of a semicircle, one is used to calculate the area of the semicircle and another helps to calculate the circumference of the semicircle.

• Area of the semicircle: The area of a semicircle can be defined as a region that is enclosed within the semicircle’s boundary. It can be said that area of the semicircle is half of the circle’s area. It can be calculated using the below-given mathematical formula:

## Area of Semicircle = 1/2 (π r2)

• Circumference of the semicircle: The circumference or perimeter of the semicircle can be defined as the length of the boundary of the semicircle. It can be calculated using the below-given mathematical formula:

Circumference of Semicircle = (1/2) π d + d

Or

= (πr + 2r)

## Bottom Line

We hope that after going through this article, all your doubts related to the concept of circle and semicircle including formulas of the circle, area of semicircle, and many other are cleared. In case you want to learn advanced-level mathematical concepts you can register at Cuemath. It is an online educational platform where you will be taught by professional and experienced teachers.

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