A circle may be round, but there are numerous angles in it. The same applies to semicircles also. To understand this, you need to understand the circle degree chart and degree measure of a semicircle. You will be amazed to know about the circle radian chart, the various uses of circles, and semicircles in your day-to-day lives.

### 1. Define Circle and Semicircle

A circle is a geometrical shape and one of the most important shapes. **Circles are perfectly round**. The word circle was derived from the Greek word Kirkos or Kuklos, which means ring or hoop. A circle can be defined as a closed two-dimensional figure with all its points at a distance forming its center.

When you **divide a circle into half along its diameter**, you will have two halves of the circle. Each of these half pieces is known as a semicircle. (See What Do You Mean By Prime Number?)

### 2. History of Circle

According to historians, people knew about circles even before the earliest records were discovered. People from early civilizations observed the sun, moon, and other celestial bodies. The **Babylonians and Sumerians kept records of the rotation of the moon and earth** on their orbits, which make up to a year of about 360 days. The historians assume that they used a sexagesimal number system. (See When Were Numbers invented?)

### 3. Properties of a Circle

- A circle with equal radii is
**congruent**. - The
**longest chord**of the circle is its diameter. - Equal chords of a circle specify
**equal angles at the center**in a circle degree chart. (See Who Invented Math?)

**4. Properties of a Semicircle**

- It has
**curved edges**, but it is not a polygon. - It is a closed 2D shape.
- It is
**exactly half of a circle**. - Its curved edge is its circumference.
- Its straight edge is the diameter.
- The
**area of a semicircle is half of the circle**from which it is made.

### 5. Parts of Circle

A circle has nine parts, as mentioned below.

- An arc is a line that joins two points present at the boundary of a circle. There are
**minor and major arcs**. The minor arc represents the shorter distance while the major arc represents the larger distance. - The
**center**is the fixed point of a circle with which you draw the circle. - A
**chord**is a straight line that joins two points at the boundary of the circle. -
**Diameter**is the line drawn from one point on the boundary to another end crossing the center is known as diameter. The length of a diameter is twice the length of its radius. (See How Many Cups are in 8 Ounces?) -
**Radius**is the fixed distance from the center to the one end of the boundary. -
**Secant**is the line joining the two points on the boundary. - In a circle degree chart, a
**sector is formed when you join two different points**from the boundary at the center. - A
**segment**is the area created when you join the ends of the arcs to the center. -
**Tangent**is the line that touches the circle at one point.

### 6. Measuring Degrees of a Circle in Circle Degree Chart

A degree circle chart is a chart that shows the position of points of a circle or a semicircle using its angle concept. Some more points related to this chart are,

- The angles in a circle are measured in degrees. You can use a protractor that is in the shape of a semicircle or a
**full circle protractor to measure the degrees of the circle.** - The protractor in semicircle form is known as a normal protractor which ranges from 0 degrees to 180 degrees. A full-circle protractor ranges from 0 degrees to 360 degrees.
- The
**difference between two angles in a normal protractor is 10 degrees**. That is, it’s like 0, 10, 20, 30…….180……360 degrees in a circle degree chart. (See 13 Different Types of Compasses)

### 7. Degree Measure of Semicircle using Circle Radian Chart

- In a circle degree chart, a
**full circle is 360 degrees****while a semicircle is 180 degrees,**known as a straight angle. - A circle of 360 degrees
**has 6 triangles of 60 degrees each.** - A quarter of the circle is 90 degrees, which is known as a
**right angle.** - The
**SI unit of angular measurement is**the**radian**. A full rotation of the circle is equal to**2π**. The value of pi (*π*) is 3.14 and 1 degree is equal to π/180 radians. (See What is pi? What is the meaning of Pi?)

### 8. Use of Circles in Architecture

You must have seen circles in architecture around the world. The **Dome of the Rock, Great Sanchi Stupa, the Duomo of the Florence Cathedral**, and Saint Peter’s Basilica in Vatican City are a few examples of the usage of circles in architecture. The shape of the circle has been adopted in windows, concrete circles, and other architectural pieces from ancient history till today. (See What Is Algebra Used For In Real Life?)

### 9. Use of Semicircles in Construction

The **Roman arch is a good example** of this, which they built to support their massive aqueducts and dome-shaped buildings. These shapes provide more support than vertical or horizontal supports or beams. (See Learn How to Zentangle)

### 10. Use of Circles and Semi Circles in Science

In science circles, are **used to design separators**. The particles move freely through the Large Hadron Corridor in Europe because of its circular shape. The formula of pi (π) is used by the National Aeronautics and Space Administration (NASA) in several applications like calculating trajectories, determining the distant plant’s size, and measuring craters. (See What are the formulas of cos 2x?)

### 11. Use of Circles in Transportation

The most crucial use of the circles in the history of transportation was the invention of the wheel. You must have noticed that the **Global Positioning System (GPS) also works by covering an area in a circular pattern**. This technology calculates the distances by identifying the points between the satellite and the point by using the circle theory and a circle degree chart. (See What does the Diamond Shaped Traffic Sign Mean?)

### 12. Use of Circles and Semicircles in Video Games

Circle theorems and other geometrical concepts are used in the development of virtual worlds in video games. The knowledge of circle theory is used by developers to transfer their two-dimensional ideas into three-dimensional ideas. (See Pac Man Ghost Game)

### 13. Other Uses of Circles and Semicircles

These shapes are put to use in day-to-day life also. The fan hub, dishes, ornaments, coins, hula-hoop, vinyl record, compact disks, eatables or food items, **dartboard, clock, buttons, giant wheel, and roundabouts** are some examples of uses of the circle. Japanese fans, analog speedometers, windows, tacos, tunnels, napkin holders, pizza, and mats are a few examples of the use of semicircles in daily life. (See Burrito vs Taco vs Fajita)

So today you got to know about the circle degree chart, circle radian chart, and degree measure of the semicircle. Do share this article with your family and friends so that they will also understand the concept of the circle degree chart.