Parts of a circle, with definition and how to find them

This article will be about The part of a circle, with the definition of each part and the way to find them.

Definition of a circle

A circle is a geometric shape that is formed by a curved line which ends in the same point it started. A circle can be seen in other geometry branches, even when we cannot appreciate it, but there are operations that belongs to the circle environment and these have also application in other studies, this is why it is important to study carefully the basic concepts of the circle.

A circle has various parts that characterize it, where each of the parts is connected with the others, this means that, based only on one part we can find the rest of the parts, just with the right formulas.

The parts of a circle does not share characteristics with others circles, this means that if a circle has a part that is “x” long, then it cannot be another circle with that same part equals to “x” and the rest of the parts are different, unless the circles are identical, here we can see that the parts of a circle are strictly connected with each other.

Circumference

The circumference of a circle is the perimeter, that is the border line that forms the circle, normally a circumference is confused with the circle itself, it is very common to make these two a synonym that we can use the term circumference to refer to a circle, but the circumference is only the line that forms the circle.

As we explained before, each part of the circle is connect with the rest, this is why the formulas to find a part of the circle will change depending on the parts we already know, in the case of finding the circumference, these are the formulas.

• Circumference = diameter * PI
• Circumference = 2radius * PI

Something we have to take into account is that there is not a thing such as a perfect circumference, at least physically visible, just in the imagination, this is because it is impossible to draw, design or build a circumference that is perfect in every part of it.

Center

The center is a point inside a circle, which is at the same distance to every point of the circumference.

There are many ways to determine the exact position of the center of a circle, most of the ways are going to require the use of a rule, the easiest way to do it is to draw a square around the circle and when we have drawn the square we have to draw lines from one corner of the square to the opposite corner, in the 4 corners, and the point where the lines intercept each other, there is the center of the circle.

Radius

The radius of a circle is a line that goes from the center of the circle to a part of the circumference, no matter in which direction the line is drawn, it will always be the same length.

The radius is the most used part of the circle and this is represented by the letter “r”, the radius is always half the longitude of the diameter and the formulas to find it are the followings.

• Diametro = Circunferencia / PI
• Radio = Circunferencia / 2 PI

Diameter

The diameter is a line that goes from one edge of the circumference to another, this line has to pass through the center so it can be the diameter, otherwise, this line would not represent the diameter.

The diameter is a line that divides the circle in two equal parts, and it is twice the length of the radius of the circle, the formula to find the diameter is:

• Diameter = 2 radius

Chord and arc

The chord and the arc of a circle are not fixed parts, as it could be the radius that it is only one, or the circumference or diameter, both chord and arc could be different in only one circle because they are parts that will depend on the thing we want to know.

PI

Another part commonly known in a circle is PI, PI is the relation between the circumference of a circle and the diameter of the circle, the approximate value of PI is 3.1416, in reality PI is a rational number, this means that has infinite decimals.

The number PI, besides being use in circles, is also found in many other branches that have nothing to do with geometry, because PI is a number that appears in other topics, but the common definition of PI is the one that includes the diameter and circumference of a circle.

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